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-\input texinfo @c -*-texinfo-*-
-@c %**start of header
-@setfilename diff.info
-@settitle Comparing and Merging Files
-@setchapternewpage odd
-@c %**end of header
-
-@ifinfo
-This file documents the the GNU @code{diff}, @code{diff3}, @code{sdiff},
-and @code{cmp} commands for showing the differences between text files
-and the @code{patch} command for using their output to update files.
-
-Copyright (C) 1992, 1993, 1994 Free Software Foundation, Inc.
-
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
-
-@ignore
-Permission is granted to process this file through TeX and print the
-results, provided the printed document carries copying permission
-notice identical to this one except for the removal of this paragraph
-(this paragraph not being relevant to the printed manual).
-
-@end ignore
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the entire
-resulting derived work is distributed under the terms of a permission
-notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be stated in a translation approved
-by the Foundation.
-@end ifinfo
-
-@titlepage
-@title Comparing and Merging Files
-@subtitle @code{diff}, @code{diff3}, @code{sdiff}, @code{cmp}, and @code{patch}
-@subtitle Edition 1.3, for @code{diff} 2.5 and @code{patch} 2.1
-@subtitle September 1993
-@author by David MacKenzie, Paul Eggert, and Richard Stallman
-
-@page
-@vskip 0pt plus 1filll
-Copyright @copyright{} 1992, 1993, 1994 Free Software Foundation, Inc.
-
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
-
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the entire
-resulting derived work is distributed under the terms of a permission
-notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be stated in a translation approved
-by the Foundation.
-@end titlepage
-
-@node Top, , , (dir)
-
-@ifinfo
-This file documents the the GNU @code{diff}, @code{diff3}, @code{sdiff},
-and @code{cmp} commands for showing the differences between text files
-and the @code{patch} command for using their output to update files.
-
-This is Edition 1.2, for @code{diff} 2.4 and @code{patch} 2.1.
-@end ifinfo
-
-@menu
-* Overview::		Preliminary information.
-
-* Comparison::		What file comparison means.
-* Output Formats::	Formats for difference reports.
-* Comparing Directories::	Comparing files and directories.
-* Adjusting Output::	Making @code{diff} output prettier.
-* diff Performance::	Making @code{diff} smarter or faster.
-* Comparing Three Files:: Formats for three-way difference reports.
-
-* diff3 Merging::	Merging from a common ancestor.
-* Interactive Merging::	Interactive merging with @code{sdiff}.
-* Merging with patch::	Using @code{patch} to change old files into new ones.
-* Making Patches::	Tips for making patch distributions.
-
-* Invoking cmp::	How to run @code{cmp} and a summary of its options.
-* Invoking diff::	How to run @code{diff} and a summary of its options.
-* Invoking diff3::	How to run @code{diff3} and a summary of its options.
-* Invoking patch::	How to run @code{patch} and a summary of its options.
-* Invoking sdiff::	How to run @code{sdiff} and a summary of its options.
-
-* Incomplete Lines::	Lines that lack trailing newlines.
-* Projects::		If you think you've found a bug or other shortcoming.
-
-* Concept Index::	Index of concepts.
-@end menu
-
-@node Overview, Comparison, , Top
-@unnumbered Overview
-@cindex overview of @code{diff} and @code{patch}
-
-Computer users often find occasion to ask how two files differ.  Perhaps
-one file is a newer version of the other file.  Or maybe the two files
-started out as identical copies but were changed by different people.
-
-You can use the @code{diff} command to show differences between two
-files, or each corresponding file in two directories.  @code{diff}
-outputs differences between files line by line in any of several
-formats, selectable by command line options.  This set of differences is
-often called a @dfn{diff} or @dfn{patch}.  For files that are identical,
-@code{diff} normally produces no output; for binary (non-text) files,
-@code{diff} normally reports only that they are different.
-
-You can use the @code{cmp} command to show the offsets and line numbers
-where two files differ.  @code{cmp} can also show all the characters
-that differ between the two files, side by side.  Another way to compare
-two files character by character is the Emacs command @kbd{M-x
-compare-windows}.  @xref{Other Window, , Other Window, emacs, The GNU
-Emacs Manual}, for more information on that command.
-
-You can use the @code{diff3} command to show differences among three
-files.  When two people have made independent changes to a common
-original, @code{diff3} can report the differences between the original
-and the two changed versions, and can produce a merged file that
-contains both persons' changes together with warnings about conflicts.
-
-You can use the @code{sdiff} command to merge two files interactively.
-
-You can use the set of differences produced by @code{diff} to distribute
-updates to text files (such as program source code) to other people.
-This method is especially useful when the differences are small compared
-to the complete files.  Given @code{diff} output, you can use the
-@code{patch} program to update, or @dfn{patch}, a copy of the file.  If you
-think of @code{diff} as subtracting one file from another to produce
-their difference, you can think of @code{patch} as adding the difference
-to one file to reproduce the other.
-
-This manual first concentrates on making diffs, and later shows how to
-use diffs to update files.
-
-GNU @code{diff} was written by Mike Haertel, David Hayes, Richard
-Stallman, Len Tower, and Paul Eggert.  Wayne Davison designed and
-implemented the unified output format.  The basic algorithm is described
-in ``An O(ND) Difference Algorithm and its Variations'', Eugene W. Myers,
-@cite{Algorithmica} Vol.@: 1 No.@: 2, 1986, pp.@: 251--266; and in ``A File
-Comparison Program'', Webb Miller and Eugene W. Myers,
-@cite{Software---Practice and Experience} Vol.@: 15 No.@: 11, 1985,
-pp.@: 1025--1040.
-@c From: "Gene Myers" <gene@cs.arizona.edu>
-@c They are about the same basic algorithm; the Algorithmica
-@c paper gives a rigorous treatment and the sub-algorithm for
-@c delivering scripts and should be the primary reference, but
-@c both should be mentioned.
-The algorithm was independently discovered as described in
-``Algorithms for Approximate String Matching'',
-E. Ukkonen, @cite{Information and Control} Vol.@: 64, 1985, pp.@: 100--118.
-@c From: "Gene Myers" <gene@cs.arizona.edu>
-@c Date: Wed, 29 Sep 1993 08:27:55 MST
-@c Ukkonen should be given credit for also discovering the algorithm used
-@c in GNU diff.
-
-GNU @code{diff3} was written by Randy Smith.  GNU @code{sdiff} was
-written by Thomas Lord.  GNU @code{cmp} was written by Torbjorn Granlund
-and David MacKenzie.
-
-@code{patch} was written mainly by Larry Wall; the GNU enhancements were
-written mainly by Wayne Davison and David MacKenzie.  Parts of this
-manual are adapted from a manual page written by Larry Wall, with his
-permission.
-
-@node Comparison, Output Formats, Overview, Top
-@chapter What Comparison Means
-@cindex introduction
-
-There are several ways to think about the differences between two files.
-One way to think of the differences is as a series of lines that were
-deleted from, inserted in, or changed in one file to produce the other
-file.  @code{diff} compares two files line by line, finds groups of
-lines that differ, and reports each group of differing lines.  It can
-report the differing lines in several formats, which have different
-purposes.
-
-GNU @code{diff} can show whether files are different without detailing
-the differences.  It also provides ways to suppress certain kinds of
-differences that are not important to you.  Most commonly, such
-differences are changes in the amount of white space between words or
-lines.  @code{diff} also provides ways to suppress differences in
-alphabetic case or in lines that match a regular expression that you
-provide.  These options can accumulate; for example, you can ignore
-changes in both white space and alphabetic case.
-
-Another way to think of the differences between two files is as a
-sequence of pairs of characters that can be either identical or
-different.  @code{cmp} reports the differences between two files
-character by character, instead of line by line.  As a result, it is
-more useful than @code{diff} for comparing binary files.  For text
-files, @code{cmp} is useful mainly when you want to know only whether
-two files are identical.
-
-To illustrate the effect that considering changes character by character
-can have compared with considering them line by line, think of what
-happens if a single newline character is added to the beginning of a
-file.  If that file is then compared with an otherwise identical file
-that lacks the newline at the beginning, @code{diff} will report that a
-blank line has been added to the file, while @code{cmp} will report that
-almost every character of the two files differs.
-
-@code{diff3} normally compares three input files line by line, finds
-groups of lines that differ, and reports each group of differing lines.
-Its output is designed to make it easy to inspect two different sets of
-changes to the same file.
-
-@menu
-* Hunks::		Groups of differing lines.
-* White Space::		Suppressing differences in white space.
-* Blank Lines::		Suppressing differences in blank lines.
-* Case Folding::	Suppressing differences in alphabetic case.
-* Specified Folding::	Suppressing differences that match regular expressions.
-* Brief::		Summarizing which files are different.
-* Binary::		Comparing binary files or forcing text comparisons.
-@end menu
-
-@node Hunks, White Space, , Comparison
-@section Hunks
-@cindex hunks
-
-When comparing two files, @code{diff} finds sequences of lines common to
-both files, interspersed with groups of differing lines called
-@dfn{hunks}.  Comparing two identical files yields one sequence of
-common lines and no hunks, because no lines differ.  Comparing two
-entirely different files yields no common lines and one large hunk that
-contains all lines of both files.  In general, there are many ways to
-match up lines between two given files.  @code{diff} tries to minimize
-the total hunk size by finding large sequences of common lines
-interspersed with small hunks of differing lines.
-
-For example, suppose the file @file{F} contains the three lines
-@samp{a}, @samp{b}, @samp{c}, and the file @file{G} contains the same
-three lines in reverse order @samp{c}, @samp{b}, @samp{a}.  If
-@code{diff} finds the line @samp{c} as common, then the command
-@samp{diff F G} produces this output:
-
-@example
-1,2d0
-< a
-< b
-3a2,3
-> b
-> a
-@end example
-
-@noindent
-But if @code{diff} notices the common line @samp{b} instead, it produces
-this output:
-
-@example
-1c1
-< a
----
-> c
-3c3
-< c
----
-> a
-@end example
-
-@noindent
-It is also possible to find @samp{a} as the common line.  @code{diff}
-does not always find an optimal matching between the files; it takes
-shortcuts to run faster.  But its output is usually close to the
-shortest possible.  You can adjust this tradeoff with the
-@samp{--minimal} option (@pxref{diff Performance}).
-
-@node White Space, Blank Lines, Hunks, Comparison
-@section Suppressing Differences in Blank and Tab Spacing
-@cindex blank and tab difference suppression
-@cindex tab and blank difference suppression
-
-The @samp{-b} and @samp{--ignore-space-change} options ignore white space
-at line end, and considers all other sequences of one or more
-white space characters to be equivalent.  With these options,
-@code{diff} considers the following two lines to be equivalent, where
-@samp{$} denotes the line end:
-
-@example
-Here lyeth  muche rychnesse  in lytell space.   -- John Heywood$
-Here lyeth muche rychnesse in lytell space. -- John Heywood   $
-@end example
-
-The @samp{-w} and @samp{--ignore-all-space} options are stronger than
-@samp{-b}.  They ignore difference even if one file has white space where
-the other file has none.  @dfn{White space} characters include
-tab, newline, vertical tab, form feed, carriage return, and space;
-some locales may define additional characters to be white space.
-With these options, @code{diff} considers the
-following two lines to be equivalent, where @samp{$} denotes the line
-end and @samp{^M} denotes a carriage return:
-
-@example
-Here lyeth  muche  rychnesse in lytell space.--  John Heywood$
-  He relyeth much erychnes  seinly tells pace.  --John Heywood   ^M$
-@end example
-
-@node Blank Lines, Case Folding, White Space, Comparison
-@section Suppressing Differences in Blank Lines
-@cindex blank line difference suppression
-
-The @samp{-B} and @samp{--ignore-blank-lines} options ignore insertions
-or deletions of blank lines.  These options normally affect only lines
-that are completely empty; they do not affect lines that look empty but
-contain space or tab characters.  With these options, for example, a
-file containing
-@example
-1.  A point is that which has no part.
-
-2.  A line is breadthless length.
--- Euclid, The Elements, I
-@end example
-@noindent
-is considered identical to a file containing
-@example
-1.  A point is that which has no part.
-2.  A line is breadthless length.
-
-
--- Euclid, The Elements, I
-@end example
-
-@node Case Folding, Specified Folding, Blank Lines, Comparison
-@section Suppressing Case Differences
-@cindex case difference suppression
-
-GNU @code{diff} can treat lowercase letters as equivalent to their
-uppercase counterparts, so that, for example, it considers @samp{Funky
-Stuff}, @samp{funky STUFF}, and @samp{fUNKy stuFf} to all be the same.
-To request this, use the @samp{-i} or @samp{--ignore-case} option.
-
-@node Specified Folding, Brief, Case Folding, Comparison
-@section Suppressing Lines Matching a Regular Expression
-@cindex regular expression suppression
-
-To ignore insertions and deletions of lines that match a regular
-expression, use the @samp{-I @var{regexp}} or
-@samp{--ignore-matching-lines=@var{regexp}} option.  You should escape
-regular expressions that contain shell metacharacters to prevent the
-shell from expanding them.  For example, @samp{diff -I '^[0-9]'} ignores
-all changes to lines beginning with a digit.
-
-However, @samp{-I} only ignores the insertion or deletion of lines that
-contain the regular expression if every changed line in the hunk---every
-insertion and every deletion---matches the regular expression.  In other
-words, for each nonignorable change, @code{diff} prints the complete set
-of changes in its vicinity, including the ignorable ones.
-
-You can specify more than one regular expression for lines to ignore by
-using more than one @samp{-I} option.  @code{diff} tries to match each
-line against each regular expression, starting with the last one given.
-
-@node Brief, Binary, Specified Folding, Comparison
-@section Summarizing Which Files Differ
-@cindex summarizing which files differ
-@cindex brief difference reports
-
-When you only want to find out whether files are different, and you
-don't care what the differences are, you can use the summary output
-format.  In this format, instead of showing the differences between the
-files, @code{diff} simply reports whether files differ.  The @samp{-q}
-and @samp{--brief} options select this output format.
-
-This format is especially useful when comparing the contents of two
-directories.  It is also much faster than doing the normal line by line
-comparisons, because @code{diff} can stop analyzing the files as soon as
-it knows that there are any differences.
-
-You can also get a brief indication of whether two files differ by using
-@code{cmp}.  For files that are identical, @code{cmp} produces no
-output.  When the files differ, by default, @code{cmp} outputs the byte
-offset and line number where the first difference occurs.  You can use
-the @samp{-s} option to suppress that information, so that @code{cmp}
-produces no output and reports whether the files differ using only its
-exit status (@pxref{Invoking cmp}).
-
-@c Fix this.
-Unlike @code{diff}, @code{cmp} cannot compare directories; it can only
-compare two files.
-
-@node Binary, , Brief, Comparison
-@section Binary Files and Forcing Text Comparisons
-@cindex binary file diff
-@cindex text versus binary diff
-
-If @code{diff} thinks that either of the two files it is comparing is
-binary (a non-text file), it normally treats that pair of files much as
-if the summary output format had been selected (@pxref{Brief}), and
-reports only that the binary files are different.  This is because line
-by line comparisons are usually not meaningful for binary files.
-
-@code{diff} determines whether a file is text or binary by checking the
-first few bytes in the file; the exact number of bytes is system
-dependent, but it is typically several thousand.  If every character in
-that part of the file is non-null, @code{diff} considers the file to be
-text; otherwise it considers the file to be binary.
-
-Sometimes you might want to force @code{diff} to consider files to be
-text.  For example, you might be comparing text files that contain
-null characters; @code{diff} would erroneously decide that those are
-non-text files.  Or you might be comparing documents that are in a
-format used by a word processing system that uses null characters to
-indicate special formatting.  You can force @code{diff} to consider all
-files to be text files, and compare them line by line, by using the
-@samp{-a} or @samp{--text} option.  If the files you compare using this
-option do not in fact contain text, they will probably contain few
-newline characters, and the @code{diff} output will consist of hunks
-showing differences between long lines of whatever characters the files
-contain.
-
-You can also force @code{diff} to consider all files to be binary files,
-and report only whether they differ (but not how).  Use the
-@samp{--brief} option for this.
-
-In operating systems that distinguish between text and binary files,
-@code{diff} normally reads and writes all data as text.  Use the
-@samp{--binary} option to force @code{diff} to read and write binary
-data instead.  This option has no effect on a Posix-compliant system
-like GNU or traditional Unix.  However, many personal computer
-operating systems represent the end of a line with a carriage return
-followed by a newline.  On such systems, @code{diff} normally ignores
-these carriage returns on input and generates them at the end of each
-output line, but with the @samp{--binary} option @code{diff} treats
-each carriage return as just another input character, and does not
-generate a carriage return at the end of each output line.  This can be
-useful when dealing with non-text files that are meant to be
-interchanged with Posix-compliant systems.
-
-If you want to compare two files byte by byte, you can use the
-@code{cmp} program with the @samp{-l} option to show the values of each
-differing byte in the two files.  With GNU @code{cmp}, you can also use
-the @samp{-c} option to show the ASCII representation of those bytes.
-@xref{Invoking cmp}, for more information.
-
-If @code{diff3} thinks that any of the files it is comparing is binary
-(a non-text file), it normally reports an error, because such
-comparisons are usually not useful.  @code{diff3} uses the same test as
-@code{diff} to decide whether a file is binary.  As with @code{diff}, if
-the input files contain a few non-text characters but otherwise are like
-text files, you can force @code{diff3} to consider all files to be text
-files and compare them line by line by using the @samp{-a} or
-@samp{--text} options.
-
-@node Output Formats, Comparing Directories, Comparison, Top
-@chapter @code{diff} Output Formats
-@cindex output formats
-@cindex format of @code{diff} output
-
-@code{diff} has several mutually exclusive options for output format.
-The following sections describe each format, illustrating how
-@code{diff} reports the differences between two sample input files.
-
-@menu
-* Sample diff Input::	Sample @code{diff} input files for examples.
-* Normal::		Showing differences without surrounding text.
-* Context::		Showing differences with the surrounding text.
-* Side by Side::        Showing differences in two columns.
-* Scripts::		Generating scripts for other programs.
-* If-then-else::	Merging files with if-then-else.
-@end menu
-
-@node Sample diff Input, Normal, , Output Formats
-@section Two Sample Input Files
-@cindex @code{diff} sample input
-@cindex sample input for @code{diff}
-
-Here are two sample files that we will use in numerous examples to
-illustrate the output of @code{diff} and how various options can change
-it.
-
-This is the file @file{lao}:
-
-@example
-The Way that can be told of is not the eternal Way;
-The name that can be named is not the eternal name.
-The Nameless is the origin of Heaven and Earth;
-The Named is the mother of all things.
-Therefore let there always be non-being,
-  so we may see their subtlety,
-And let there always be being,
-  so we may see their outcome.
-The two are the same,
-But after they are produced,
-  they have different names.
-@end example
-
-This is the file @file{tzu}:
-
-@example
-The Nameless is the origin of Heaven and Earth;
-The named is the mother of all things.
-
-Therefore let there always be non-being,
-  so we may see their subtlety,
-And let there always be being,
-  so we may see their outcome.
-The two are the same,
-But after they are produced,
-  they have different names.
-They both may be called deep and profound.
-Deeper and more profound,
-The door of all subtleties!
-@end example
-
-In this example, the first hunk contains just the first two lines of
-@file{lao}, the second hunk contains the fourth line of @file{lao}
-opposing the second and third lines of @file{tzu}, and the last hunk
-contains just the last three lines of @file{tzu}.
-
-@node Normal, Context, Sample diff Input, Output Formats
-@section Showing Differences Without Context
-@cindex normal output format
-@cindex @samp{<} output format
-
-The ``normal'' @code{diff} output format shows each hunk of differences
-without any surrounding context.  Sometimes such output is the clearest
-way to see how lines have changed, without the clutter of nearby
-unchanged lines (although you can get similar results with the context
-or unified formats by using 0 lines of context).  However, this format
-is no longer widely used for sending out patches; for that purpose, the
-context format (@pxref{Context Format}) and the unified format
-(@pxref{Unified Format}) are superior.  Normal format is the default for
-compatibility with older versions of @code{diff} and the Posix standard.
-
-@menu
-* Detailed Normal::	A detailed description of normal output format.
-* Example Normal::	Sample output in the normal format.
-@end menu
-
-@node Detailed Normal, Example Normal, , Normal
-@subsection Detailed Description of Normal Format
-
-The normal output format consists of one or more hunks of differences;
-each hunk shows one area where the files differ.  Normal format hunks
-look like this:
-
-@example
-@var{change-command}
-< @var{from-file-line}
-< @var{from-file-line}@dots{}
----
-> @var{to-file-line}
-> @var{to-file-line}@dots{}
-@end example
-
-There are three types of change commands.  Each consists of a line
-number or comma-separated range of lines in the first file, a single
-character indicating the kind of change to make, and a line number or
-comma-separated range of lines in the second file.  All line numbers are
-the original line numbers in each file.  The types of change commands
-are:
-
-@table @samp
-@item @var{l}a@var{r}
-Add the lines in range @var{r} of the second file after line @var{l} of
-the first file.  For example, @samp{8a12,15} means append lines 12--15
-of file 2 after line 8 of file 1; or, if changing file 2 into file 1,
-delete lines 12--15 of file 2.
-
-@item @var{f}c@var{t}
-Replace the lines in range @var{f} of the first file with lines in range
-@var{t} of the second file.  This is like a combined add and delete, but
-more compact.  For example, @samp{5,7c8,10} means change lines 5--7 of
-file 1 to read as lines 8--10 of file 2; or, if changing file 2 into
-file 1, change lines 8--10 of file 2 to read as lines 5--7 of file 1.
-
-@item @var{r}d@var{l}
-Delete the lines in range @var{r} from the first file; line @var{l} is where
-they would have appeared in the second file had they not been deleted.
-For example, @samp{5,7d3} means delete lines 5--7 of file 1; or, if
-changing file 2 into file 1, append lines 5--7 of file 1 after line 3 of
-file 2.
-@end table
-
-@node Example Normal, , Detailed Normal, Normal
-@subsection An Example of Normal Format
-
-Here is the output of the command @samp{diff lao tzu}
-(@pxref{Sample diff Input}, for the complete contents of the two files).
-Notice that it shows only the lines that are different between the two
-files.
-
-@example
-1,2d0
-< The Way that can be told of is not the eternal Way;
-< The name that can be named is not the eternal name.
-4c2,3
-< The Named is the mother of all things.
----
-> The named is the mother of all things.
-> 
-11a11,13
-> They both may be called deep and profound.
-> Deeper and more profound,
-> The door of all subtleties!
-@end example
-
-@node Context, Side by Side, Normal, Output Formats
-@section Showing Differences in Their Context
-@cindex context output format
-@cindex @samp{!} output format
-
-Usually, when you are looking at the differences between files, you will
-also want to see the parts of the files near the lines that differ, to
-help you understand exactly what has changed.  These nearby parts of the
-files are called the @dfn{context}.
-
-GNU @code{diff} provides two output formats that show context around the
-differing lines: @dfn{context format} and @dfn{unified format}.  It can
-optionally show in which function or section of the file the differing
-lines are found.
-
-If you are distributing new versions of files to other people in the
-form of @code{diff} output, you should use one of the output formats
-that show context so that they can apply the diffs even if they have
-made small changes of their own to the files.  @code{patch} can apply
-the diffs in this case by searching in the files for the lines of
-context around the differing lines; if those lines are actually a few
-lines away from where the diff says they are, @code{patch} can adjust
-the line numbers accordingly and still apply the diff correctly.
-@xref{Imperfect}, for more information on using @code{patch} to apply
-imperfect diffs.
-
-@menu
-* Context Format::	An output format that shows surrounding lines.
-* Unified Format::	A more compact output format that shows context.
-* Sections::		Showing which sections of the files differences are in.
-* Alternate Names::	Showing alternate file names in context headers.
-@end menu
-
-@node Context Format, Unified Format, , Context
-@subsection Context Format
-
-The context output format shows several lines of context around the
-lines that differ.  It is the standard format for distributing updates
-to source code.
-
-To select this output format, use the @samp{-C @var{lines}},
-@samp{--context@r{[}=@var{lines}@r{]}}, or @samp{-c} option.  The
-argument @var{lines} that some of these options take is the number of
-lines of context to show.  If you do not specify @var{lines}, it
-defaults to three.  For proper operation, @code{patch} typically needs
-at least two lines of context.
-
-@menu
-* Detailed Context::	A detailed description of the context output format.
-* Example Context::	Sample output in context format.
-* Less Context::	Another sample with less context.
-@end menu
-
-@node Detailed Context, Example Context, , Context Format
-@subsubsection Detailed Description of Context Format
-
-The context output format starts with a two-line header, which looks
-like this:
-
-@example
-*** @var{from-file} @var{from-file-modification-time}
---- @var{to-file} @var{to-file-modification time}
-@end example
-
-@noindent
-You can change the header's content with the @samp{-L @var{label}} or
-@samp{--label=@var{label}} option; see @ref{Alternate Names}.
-
-Next come one or more hunks of differences; each hunk shows one area
-where the files differ.  Context format hunks look like this:
-
-@example
-***************
-*** @var{from-file-line-range} ****
-  @var{from-file-line}
-  @var{from-file-line}@dots{}
---- @var{to-file-line-range} ----
-  @var{to-file-line}
-  @var{to-file-line}@dots{}
-@end example
-
-The lines of context around the lines that differ start with two space
-characters.  The lines that differ between the two files start with one
-of the following indicator characters, followed by a space character:
-
-@table @samp
-@item !
-A line that is part of a group of one or more lines that changed between
-the two files.  There is a corresponding group of lines marked with
-@samp{!} in the part of this hunk for the other file.
-
-@item +
-An ``inserted'' line in the second file that corresponds to nothing in
-the first file.
-
-@item -
-A ``deleted'' line in the first file that corresponds to nothing in the
-second file.
-@end table
-
-If all of the changes in a hunk are insertions, the lines of
-@var{from-file} are omitted.  If all of the changes are deletions, the
-lines of @var{to-file} are omitted.
-
-@node Example Context, Less Context, Detailed Context, Context Format
-@subsubsection An Example of Context Format
-
-Here is the output of @samp{diff -c lao tzu} (@pxref{Sample diff Input},
-for the complete contents of the two files).  Notice that up to three
-lines that are not different are shown around each line that is
-different; they are the context lines.  Also notice that the first two
-hunks have run together, because their contents overlap.
-
-@example
-*** lao	Sat Jan 26 23:30:39 1991
---- tzu	Sat Jan 26 23:30:50 1991
-***************
-*** 1,7 ****
-- The Way that can be told of is not the eternal Way;
-- The name that can be named is not the eternal name.
-  The Nameless is the origin of Heaven and Earth;
-! The Named is the mother of all things.
-  Therefore let there always be non-being,
-    so we may see their subtlety,
-  And let there always be being,
---- 1,6 ----
-  The Nameless is the origin of Heaven and Earth;
-! The named is the mother of all things.
-! 
-  Therefore let there always be non-being,
-    so we may see their subtlety,
-  And let there always be being,
-***************
-*** 9,11 ****
---- 8,13 ----
-  The two are the same,
-  But after they are produced,
-    they have different names.
-+ They both may be called deep and profound.
-+ Deeper and more profound,
-+ The door of all subtleties!
-@end example
-
-@node Less Context, , Example Context, Context Format
-@subsubsection An Example of Context Format with Less Context
-
-Here is the output of @samp{diff --context=1 lao tzu} (@pxref{Sample
-diff Input}, for the complete contents of the two files).  Notice that
-at most one context line is reported here.
-
-@example
-*** lao	Sat Jan 26 23:30:39 1991
---- tzu	Sat Jan 26 23:30:50 1991
-***************
-*** 1,5 ****
-- The Way that can be told of is not the eternal Way;
-- The name that can be named is not the eternal name.
-  The Nameless is the origin of Heaven and Earth;
-! The Named is the mother of all things.
-  Therefore let there always be non-being,
---- 1,4 ----
-  The Nameless is the origin of Heaven and Earth;
-! The named is the mother of all things.
-! 
-  Therefore let there always be non-being,
-***************
-*** 11 ****
---- 10,13 ----
-    they have different names.
-+ They both may be called deep and profound.
-+ Deeper and more profound,
-+ The door of all subtleties!
-@end example
-
-@node Unified Format, Sections, Context Format, Context
-@subsection Unified Format
-@cindex unified output format
-@cindex @samp{+-} output format
-
-The unified output format is a variation on the context format that is
-more compact because it omits redundant context lines.  To select this
-output format, use the @samp{-U @var{lines}},
-@samp{--unified@r{[}=@var{lines}@r{]}}, or @samp{-u}
-option.  The argument @var{lines} is the number of lines of context to
-show.  When it is not given, it defaults to three.
-
-At present, only GNU @code{diff} can produce this format and only GNU
-@code{patch} can automatically apply diffs in this format.  For proper
-operation, @code{patch} typically needs at least two lines of context.
-
-@menu
-* Detailed Unified::	A detailed description of unified format.
-* Example Unified::	Sample output in unified format.
-@end menu
-
-@node Detailed Unified, Example Unified, , Unified Format
-@subsubsection Detailed Description of Unified Format
-
-The unified output format starts with a two-line header, which looks
-like this:
-
-@example
---- @var{from-file} @var{from-file-modification-time}
-+++ @var{to-file} @var{to-file-modification-time}
-@end example
-
-@noindent
-You can change the header's content with the @samp{-L @var{label}} or
-@samp{--label=@var{label}} option; see @xref{Alternate Names}.
-
-Next come one or more hunks of differences; each hunk shows one area
-where the files differ.  Unified format hunks look like this:
-
-@example
-@@@@ @var{from-file-range} @var{to-file-range} @@@@
- @var{line-from-either-file}
- @var{line-from-either-file}@dots{}
-@end example
-
-The lines common to both files begin with a space character.  The lines
-that actually differ between the two files have one of the following
-indicator characters in the left column:
-
-@table @samp
-@item +
-A line was added here to the first file.
-
-@item -
-A line was removed here from the first file.
-@end table
-
-@node Example Unified, , Detailed Unified, Unified Format
-@subsubsection An Example of Unified Format
-
-Here is the output of the command @samp{diff -u lao tzu}
-(@pxref{Sample diff Input}, for the complete contents of the two files):
-
-@example
---- lao	Sat Jan 26 23:30:39 1991
-+++ tzu	Sat Jan 26 23:30:50 1991
-@@@@ -1,7 +1,6 @@@@
--The Way that can be told of is not the eternal Way;
--The name that can be named is not the eternal name.
- The Nameless is the origin of Heaven and Earth;
--The Named is the mother of all things.
-+The named is the mother of all things.
-+
- Therefore let there always be non-being,
-   so we may see their subtlety,
- And let there always be being,
-@@@@ -9,3 +8,6 @@@@
- The two are the same,
- But after they are produced,
-   they have different names.
-+They both may be called deep and profound.
-+Deeper and more profound,
-+The door of all subtleties!
-@end example
-
-@node Sections, Alternate Names, Unified Format, Context
-@subsection Showing Which Sections Differences Are in
-@cindex headings
-@cindex section headings
-
-Sometimes you might want to know which part of the files each change
-falls in.  If the files are source code, this could mean which function
-was changed.  If the files are documents, it could mean which chapter or
-appendix was changed.  GNU @code{diff} can show this by displaying the
-nearest section heading line that precedes the differing lines.  Which
-lines are ``section headings'' is determined by a regular expression.
-
-@menu
-* Specified Headings::	Showing headings that match regular expressions.
-* C Function Headings::	Showing headings of C functions.
-@end menu
-
-@node Specified Headings, C Function Headings, , Sections
-@subsubsection Showing Lines That Match Regular Expressions
-@cindex specified headings
-@cindex regular expression matching headings
-
-To show in which sections differences occur for files that are not
-source code for C or similar languages, use the @samp{-F @var{regexp}}
-or @samp{--show-function-line=@var{regexp}} option.  @code{diff}
-considers lines that match the argument @var{regexp} to be the beginning
-of a section of the file.  Here are suggested regular expressions for
-some common languages:
-
-@c Please add to this list, e.g. Fortran, Pascal.
-@table @samp
-@item ^[A-Za-z_]
-C, C++, Prolog
-@item ^(
-Lisp
-@item ^@@\(chapter\|appendix\|unnumbered\|chapheading\)
-Texinfo
-@end table
-
-This option does not automatically select an output format; in order to
-use it, you must select the context format (@pxref{Context Format}) or
-unified format (@pxref{Unified Format}).  In other output formats it
-has no effect.
-
-The @samp{-F} and @samp{--show-function-line} options find the nearest
-unchanged line that precedes each hunk of differences and matches the
-given regular expression.  Then they add that line to the end of the
-line of asterisks in the context format, or to the @samp{@@@@} line in
-unified format.  If no matching line exists, they leave the output for
-that hunk unchanged.  If that line is more than 40 characters long, they
-output only the first 40 characters.  You can specify more than one
-regular expression for such lines; @code{diff} tries to match each line
-against each regular expression, starting with the last one given.  This
-means that you can use @samp{-p} and @samp{-F} together, if you wish.
-
-@node C Function Headings, , Specified Headings, Sections
-@subsubsection Showing C Function Headings
-@cindex C function headings
-@cindex function headings, C
-
-To show in which functions differences occur for C and similar
-languages, you can use the @samp{-p} or @samp{--show-c-function} option.
-This option automatically defaults to the context output format
-(@pxref{Context Format}), with the default number of lines of context.
-You can override that number with @samp{-C @var{lines}} elsewhere in the
-command line.  You can override both the format and the number with
-@samp{-U @var{lines}} elsewhere in the command line.
-
-The @samp{-p} and @samp{--show-c-function} options are equivalent to
-@samp{-F'^[_a-zA-Z$]'} if the unified format is specified, otherwise
-@samp{-c -F'^[_a-zA-Z$]'} (@pxref{Specified Headings}).  GNU @code{diff}
-provides them for the sake of convenience.
-
-@node Alternate Names, , Sections, Context
-@subsection Showing Alternate File Names
-@cindex alternate file names
-@cindex file name alternates
-
-If you are comparing two files that have meaningless or uninformative
-names, you might want @code{diff} to show alternate names in the header
-of the context and unified output formats.  To do this, use the @samp{-L
-@var{label}} or @samp{--label=@var{label}} option.  The first time
-you give this option, its argument replaces the name and date of the
-first file in the header; the second time, its argument replaces the
-name and date of the second file.  If you give this option more than
-twice, @code{diff} reports an error.  The @samp{-L} option does not
-affect the file names in the @code{pr} header when the @samp{-l} or
-@samp{--paginate} option is used (@pxref{Pagination}).
-
-Here are the first two lines of the output from @samp{diff -C2
--Loriginal -Lmodified lao tzu}:
-
-@example
-*** original
---- modified
-@end example
-
-@node Side by Side, Scripts, Context, Output Formats
-@section Showing Differences Side by Side
-@cindex side by side
-@cindex two-column output
-@cindex columnar output
-
-@code{diff} can produce a side by side difference listing of two files.
-The files are listed in two columns with a gutter between them.  The
-gutter contains one of the following markers:
-
-@table @asis
-@item white space
-The corresponding lines are in common.  That is, either the lines are
-identical, or the difference is ignored because of one of the
-@samp{--ignore} options (@pxref{White Space}).
-
-@item @samp{|}
-The corresponding lines differ, and they are either both complete
-or both incomplete.
-
-@item @samp{<}
-The files differ and only the first file contains the line.
-
-@item @samp{>}
-The files differ and only the second file contains the line.
-
-@item @samp{(}
-Only the first file contains the line, but the difference is ignored.
-
-@item @samp{)}
-Only the second file contains the line, but the difference is ignored.
-
-@item @samp{\}
-The corresponding lines differ, and only the first line is incomplete.
-
-@item @samp{/}
-The corresponding lines differ, and only the second line is incomplete.
-@end table
-
-Normally, an output line is incomplete if and only if the lines that it
-contains are incomplete; @xref{Incomplete Lines}.  However, when an
-output line represents two differing lines, one might be incomplete
-while the other is not.  In this case, the output line is complete,
-but its the gutter is marked @samp{\} if the first line is incomplete,
-@samp{/} if the second line is.
-
-Side by side format is sometimes easiest to read, but it has limitations.
-It generates much wider output than usual, and truncates lines that are
-too long to fit.  Also, it relies on lining up output more heavily than
-usual, so its output looks particularly bad if you use varying
-width fonts, nonstandard tab stops, or nonprinting characters.
-
-You can use the @code{sdiff} command to interactively merge side by side
-differences.  @xref{Interactive Merging}, for more information on merging files.
-
-@menu
-* Side by Side Format::		Controlling side by side output format.
-* Example Side by Side::	Sample side by side output.
-@end menu
-
-@node Side by Side Format, Example Side by Side, , Side by Side
-@section Controlling Side by Side Format
-@cindex side by side format
-
-The @samp{-y} or @samp{--side-by-side} option selects side by side
-format.  Because side by side output lines contain two input lines, they
-are wider than usual.  They are normally 130 columns, which can fit onto
-a traditional printer line.  You can set the length of output lines with
-the @samp{-W @var{columns}} or @samp{--width=@var{columns}} option.  The
-output line is split into two halves of equal length, separated by a
-small gutter to mark differences; the right half is aligned to a tab
-stop so that tabs line up.  Input lines that are too long to fit in half
-of an output line are truncated for output.
-
-The @samp{--left-column} option prints only the left column of two
-common lines.  The @samp{--suppress-common-lines} option suppresses
-common lines entirely.
-
-@node Example Side by Side, , Side by Side Format, Side by Side
-@subsection An Example of Side by Side Format
-
-Here is the output of the command @samp{diff -y -W 72 lao tzu}
-(@pxref{Sample diff Input}, for the complete contents of the two files).
-
-@example
-The Way that can be told of is n   <
-The name that can be named is no   <
-The Nameless is the origin of He        The Nameless is the origin of He
-The Named is the mother of all t   |    The named is the mother of all t
-                                   >
-Therefore let there always be no        Therefore let there always be no
-  so we may see their subtlety,           so we may see their subtlety,
-And let there always be being,          And let there always be being,
-  so we may see their outcome.            so we may see their outcome.
-The two are the same,                   The two are the same,
-But after they are produced,            But after they are produced,
-  they have different names.              they have different names.
-                                   >    They both may be called deep and
-                                   >    Deeper and more profound,
-                                   >    The door of all subtleties!
-@end example
-
-@node Scripts, If-then-else, Side by Side, Output Formats
-@section Making Edit Scripts
-@cindex script output formats
-
-Several output modes produce command scripts for editing @var{from-file}
-to produce @var{to-file}.
-
-@menu
-* ed Scripts::		Using @code{diff} to produce commands for @code{ed}.
-* Forward ed::		Making forward @code{ed} scripts.
-* RCS::			A special @code{diff} output format used by RCS.
-@end menu
-
-@node ed Scripts, Forward ed, , Scripts
-@subsection @code{ed} Scripts
-@cindex @code{ed} script output format
-
-@code{diff} can produce commands that direct the @code{ed} text editor
-to change the first file into the second file.  Long ago, this was the
-only output mode that was suitable for editing one file into another
-automatically; today, with @code{patch}, it is almost obsolete.  Use the
-@samp{-e} or @samp{--ed} option to select this output format.
-
-Like the normal format (@pxref{Normal}), this output format does not
-show any context; unlike the normal format, it does not include the
-information necessary to apply the diff in reverse (to produce the first
-file if all you have is the second file and the diff).
-
-If the file @file{d} contains the output of @samp{diff -e old new}, then
-the command @samp{(cat d && echo w) | ed - old} edits @file{old} to make
-it a copy of @file{new}.  More generally, if @file{d1}, @file{d2},
-@dots{}, @file{dN} contain the outputs of @samp{diff -e old new1},
-@samp{diff -e new1 new2}, @dots{}, @samp{diff -e newN-1 newN},
-respectively, then the command @samp{(cat d1 d2 @dots{} dN && echo w) |
-ed - old} edits @file{old} to make it a copy of @file{newN}.
-
-@menu
-* Detailed ed::		A detailed description of @code{ed} format.
-* Example ed::		A sample @code{ed} script.
-@end menu
-
-@node Detailed ed, Example ed, , ed Scripts
-@subsubsection Detailed Description of @code{ed} Format
-
-The @code{ed} output format consists of one or more hunks of
-differences.  The changes closest to the ends of the files come first so
-that commands that change the number of lines do not affect how
-@code{ed} interprets line numbers in succeeding commands.  @code{ed}
-format hunks look like this:
-
-@example
-@var{change-command}
-@var{to-file-line}
-@var{to-file-line}@dots{}
-.
-@end example
-
-Because @code{ed} uses a single period on a line to indicate the end of
-input, GNU @code{diff} protects lines of changes that contain a single
-period on a line by writing two periods instead, then writing a
-subsequent @code{ed} command to change the two periods into one.  The
-@code{ed} format cannot represent an incomplete line, so if the second
-file ends in a changed incomplete line, @code{diff} reports an error and
-then pretends that a newline was appended.
-
-There are three types of change commands.  Each consists of a line
-number or comma-separated range of lines in the first file and a single
-character indicating the kind of change to make.  All line numbers are
-the original line numbers in the file.  The types of change commands
-are:
-
-@table @samp
-@item @var{l}a
-Add text from the second file after line @var{l} in the first file.  For
-example, @samp{8a} means to add the following lines after line 8 of file
-1.
-
-@item @var{r}c
-Replace the lines in range @var{r} in the first file with the following
-lines.  Like a combined add and delete, but more compact.  For example,
-@samp{5,7c} means change lines 5--7 of file 1 to read as the text file
-2.
-
-@item @var{r}d
-Delete the lines in range @var{r} from the first file.  For example,
-@samp{5,7d} means delete lines 5--7 of file 1.
-@end table
-
-@node Example ed, , Detailed ed, ed Scripts
-@subsubsection Example @code{ed} Script
-
-Here is the output of @samp{diff -e lao tzu} (@pxref{Sample
-diff Input}, for the complete contents of the two files):
-
-@example
-11a
-They both may be called deep and profound.
-Deeper and more profound,
-The door of all subtleties!
-.
-4c
-The named is the mother of all things.
-
-.
-1,2d
-@end example
-
-@node Forward ed, RCS, ed Scripts, Scripts
-@subsection Forward @code{ed} Scripts
-@cindex forward @code{ed} script output format
-
-@code{diff} can produce output that is like an @code{ed} script, but
-with hunks in forward (front to back) order.  The format of the commands
-is also changed slightly: command characters precede the lines they
-modify, spaces separate line numbers in ranges, and no attempt is made
-to disambiguate hunk lines consisting of a single period.  Like
-@code{ed} format, forward @code{ed} format cannot represent incomplete
-lines.
-
-Forward @code{ed} format is not very useful, because neither @code{ed}
-nor @code{patch} can apply diffs in this format.  It exists mainly for
-compatibility with older versions of @code{diff}.  Use the @samp{-f} or
-@samp{--forward-ed} option to select it.
-
-@node RCS, , Forward ed, Scripts
-@subsection RCS Scripts
-@cindex RCS script output format
-
-The RCS output format is designed specifically for use by the Revision
-Control System, which is a set of free programs used for organizing
-different versions and systems of files.  Use the @samp{-n} or
-@samp{--rcs} option to select this output format.  It is like the
-forward @code{ed} format (@pxref{Forward ed}), but it can represent
-arbitrary changes to the contents of a file because it avoids the
-forward @code{ed} format's problems with lines consisting of a single
-period and with incomplete lines.  Instead of ending text sections with
-a line consisting of a single period, each command specifies the number
-of lines it affects; a combination of the @samp{a} and @samp{d}
-commands are used instead of @samp{c}.  Also, if the second file ends
-in a changed incomplete line, then the output also ends in an
-incomplete line.
-
-Here is the output of @samp{diff -n lao tzu} (@pxref{Sample
-diff Input}, for the complete contents of the two files):
-
-@example
-d1 2
-d4 1
-a4 2
-The named is the mother of all things.
-
-a11 3
-They both may be called deep and profound.
-Deeper and more profound,
-The door of all subtleties!
-@end example
-
-@node If-then-else, , Scripts, Output Formats
-@section Merging Files with If-then-else
-@cindex merged output format
-@cindex if-then-else output format
-@cindex C if-then-else output format
-@cindex @code{ifdef} output format
-
-You can use @code{diff} to merge two files of C source code.  The output
-of @code{diff} in this format contains all the lines of both files.
-Lines common to both files are output just once; the differing parts are
-separated by the C preprocessor directives @code{#ifdef @var{name}} or
-@code{#ifndef @var{name}}, @code{#else}, and @code{#endif}.  When
-compiling the output, you select which version to use by either defining
-or leaving undefined the macro @var{name}.
-
-To merge two files, use @code{diff} with the @samp{-D @var{name}} or
-@samp{--ifdef=@var{name}} option.  The argument @var{name} is the C
-preprocessor identifier to use in the @code{#ifdef} and @code{#ifndef}
-directives.
-
-For example, if you change an instance of @code{wait (&s)} to
-@code{waitpid (-1, &s, 0)} and then merge the old and new files with
-the @samp{--ifdef=HAVE_WAITPID} option, then the affected part of your code
-might look like this:
-
-@example
-    do @{
-#ifndef HAVE_WAITPID
-        if ((w = wait (&s)) < 0  &&  errno != EINTR)
-#else /* HAVE_WAITPID */
-        if ((w = waitpid (-1, &s, 0)) < 0  &&  errno != EINTR)
-#endif /* HAVE_WAITPID */
-            return w;
-    @} while (w != child);
-@end example
-
-You can specify formats for languages other than C by using line group
-formats and line formats, as described in the next sections.
-
-@menu
-* Line Group Formats::		Formats for general if-then-else line groups.
-* Line Formats::		Formats for each line in a line group.
-* Detailed If-then-else::	A detailed description of if-then-else format.
-* Example If-then-else::	Sample if-then-else format output.
-@end menu
-
-@node Line Group Formats, Line Formats, , If-then-else
-@subsection Line Group Formats
-@cindex line group formats
-@cindex formats for if-then-else line groups
-
-Line group formats let you specify formats suitable for many
-applications that allow if-then-else input, including programming
-languages and text formatting languages.  A line group format specifies
-the output format for a contiguous group of similar lines.
-
-For example, the following command compares the TeX files @file{old}
-and @file{new}, and outputs a merged file in which old regions are
-surrounded by @samp{\begin@{em@}}-@samp{\end@{em@}} lines, and new
-regions are surrounded by @samp{\begin@{bf@}}-@samp{\end@{bf@}} lines.
-
-@example
-diff \
-   --old-group-format='\begin@{em@}
-%<\end@{em@}
-' \
-   --new-group-format='\begin@{bf@}
-%>\end@{bf@}
-' \
-   old new
-@end example
-
-The following command is equivalent to the above example, but it is a
-little more verbose, because it spells out the default line group formats.
-
-@example
-diff \
-   --old-group-format='\begin@{em@}
-%<\end@{em@}
-' \
-   --new-group-format='\begin@{bf@}
-%>\end@{bf@}
-' \
-   --unchanged-group-format='%=' \
-   --changed-group-format='\begin@{em@}
-%<\end@{em@}
-\begin@{bf@}
-%>\end@{bf@}
-' \
-   old new
-@end example
-
-Here is a more advanced example, which outputs a diff listing with
-headers containing line numbers in a ``plain English'' style.
-
-@example
-diff \
-   --unchanged-group-format='' \
-   --old-group-format='-------- %dn line%(n=1?:s) deleted at %df:
-%<' \
-   --new-group-format='-------- %dN line%(N=1?:s) added after %de:
-%>' \
-   --changed-group-format='-------- %dn line%(n=1?:s) changed at %df:
-%<-------- to:
-%>' \
-   old new
-@end example
-
-To specify a line group format, use @code{diff} with one of the options
-listed below.  You can specify up to four line group formats, one for
-each kind of line group.  You should quote @var{format}, because it
-typically contains shell metacharacters.
-
-@table @samp
-@item --old-group-format=@var{format}
-These line groups are hunks containing only lines from the first file.
-The default old group format is the same as the changed group format if
-it is specified; otherwise it is a format that outputs the line group as-is.
-
-@item --new-group-format=@var{format}
-These line groups are hunks containing only lines from the second
-file.  The default new group format is same as the the changed group
-format if it is specified; otherwise it is a format that outputs the
-line group as-is.
-
-@item --changed-group-format=@var{format}
-These line groups are hunks containing lines from both files.  The
-default changed group format is the concatenation of the old and new
-group formats.
-
-@item --unchanged-group-format=@var{format}
-These line groups contain lines common to both files.  The default
-unchanged group format is a format that outputs the line group as-is.
-@end table
-
-In a line group format, ordinary characters represent themselves;
-conversion specifications start with @samp{%} and have one of the
-following forms.
-
-@table @samp
-@item %<
-stands for the lines from the first file, including the trailing newline.
-Each line is formatted according to the old line format (@pxref{Line Formats}).
-
-@item %>
-stands for the lines from the second file, including the trailing newline.
-Each line is formatted according to the new line format.
-
-@item %=
-stands for the lines common to both files, including the trailing newline.
-Each line is formatted according to the unchanged line format.
-
-@item %%
-stands for @samp{%}.
-
-@item %c'@var{C}'
-where @var{C} is a single character, stands for @var{C}.
-@var{C} may not be a backslash or an apostrophe.
-For example, @samp{%c':'} stands for a colon, even inside
-the then-part of an if-then-else format, which a colon would
-normally terminate.
-
-@item %c'\@var{O}'
-where @var{O} is a string of 1, 2, or 3 octal digits,
-stands for the character with octal code @var{O}.
-For example, @samp{%c'\0'} stands for a null character.
-
-@item @var{F}@var{n}
-where @var{F} is a @code{printf} conversion specification and @var{n} is one
-of the following letters, stands for @var{n}'s value formatted with @var{F}.
-
-@table @samp
-@item e
-The line number of the line just before the group in the old file.
-
-@item f
-The line number of the first line in the group in the old file;
-equals @var{e} + 1.
-
-@item l
-The line number of the last line in the group in the old file.
-
-@item m
-The line number of the line just after the group in the old file;
-equals @var{l} + 1.
-
-@item n
-The number of lines in the group in the old file; equals @var{l} - @var{f} + 1.
-
-@item E, F, L, M, N
-Likewise, for lines in the new file.
-
-@end table
-
-The @code{printf} conversion specification can be @samp{%d},
-@samp{%o}, @samp{%x}, or @samp{%X}, specifying decimal, octal,
-lower case hexadecimal, or upper case hexadecimal output
-respectively.  After the @samp{%} the following options can appear in
-sequence: a @samp{-} specifying left-justification; an integer
-specifying the minimum field width; and a period followed by an
-optional integer specifying the minimum number of digits.
-For example, @samp{%5dN} prints the number of new lines in the group
-in a field of width 5 characters, using the @code{printf} format @code{"%5d"}.
-
-@item (@var{A}=@var{B}?@var{T}:@var{E})
-If @var{A} equals @var{B} then @var{T} else @var{E}.
-@var{A} and @var{B} are each either a decimal constant
-or a single letter interpreted as above.
-This format spec is equivalent to @var{T} if
-@var{A}'s value equals @var{B}'s; otherwise it is equivalent to @var{E}.
-
-For example, @samp{%(N=0?no:%dN) line%(N=1?:s)} is equivalent to
-@samp{no lines} if @var{N} (the number of lines in the group in the the
-new file) is 0, to @samp{1 line} if @var{N} is 1, and to @samp{%dN lines}
-otherwise.
-@end table
-
-@node Line Formats, Detailed If-then-else, Line Group Formats, If-then-else
-@subsection Line Formats
-@cindex line formats
-
-Line formats control how each line taken from an input file is
-output as part of a line group in if-then-else format.
-
-For example, the following command outputs text with a one-column
-change indicator to the left of the text.  The first column of output
-is @samp{-} for deleted lines, @samp{|} for added lines, and a space
-for unchanged lines.  The formats contain newline characters where
-newlines are desired on output.
-
-@example
-diff \
-   --old-line-format='-%l
-' \
-   --new-line-format='|%l
-' \
-   --unchanged-line-format=' %l
-' \
-   old new
-@end example
-
-To specify a line format, use one of the following options.  You should
-quote @var{format}, since it often contains shell metacharacters.
-
-@table @samp
-@item --old-line-format=@var{format}
-formats lines just from the first file.
-
-@item --new-line-format=@var{format}
-formats lines just from the second file.
-
-@item --unchanged-line-format=@var{format}
-formats lines common to both files.
-
-@item --line-format=@var{format}
-formats all lines; in effect, it sets all three above options simultaneously.
-@end table
-
-In a line format, ordinary characters represent themselves;
-conversion specifications start with @samp{%} and have one of the
-following forms.
-
-@table @samp
-@item %l
-stands for the the contents of the line, not counting its trailing
-newline (if any).  This format ignores whether the line is incomplete;
-@xref{Incomplete Lines}.
-
-@item %L
-stands for the the contents of the line, including its trailing newline
-(if any).  If a line is incomplete, this format preserves its
-incompleteness.
-
-@item %%
-stands for @samp{%}.
-
-@item %c'@var{C}'
-where @var{C} is a single character, stands for @var{C}.
-@var{C} may not be a backslash or an apostrophe.
-For example, @samp{%c':'} stands for a colon.
-
-@item %c'\@var{O}'
-where @var{O} is a string of 1, 2, or 3 octal digits,
-stands for the character with octal code @var{O}.
-For example, @samp{%c'\0'} stands for a null character.
-
-@item @var{F}n
-where @var{F} is a @code{printf} conversion specification,
-stands for the line number formatted with @var{F}.
-For example, @samp{%.5dn} prints the line number using the
-@code{printf} format @code{"%.5d"}.  @xref{Line Group Formats}, for
-more about printf conversion specifications.
-
-@end table
-
-The default line format is @samp{%l} followed by a newline character.
-
-If the input contains tab characters and it is important that they line
-up on output, you should ensure that @samp{%l} or @samp{%L} in a line
-format is just after a tab stop (e.g.@: by preceding @samp{%l} or
-@samp{%L} with a tab character), or you should use the @samp{-t} or
-@samp{--expand-tabs} option.
-
-Taken together, the line and line group formats let you specify many
-different formats.  For example, the following command uses a format
-similar to @code{diff}'s normal format.  You can tailor this command
-to get fine control over @code{diff}'s output.
-
-@example
-diff \
-   --old-line-format='< %l
-' \
-   --new-line-format='> %l
-' \
-   --old-group-format='%df%(f=l?:,%dl)d%dE
-%<' \
-   --new-group-format='%dea%dF%(F=L?:,%dL)
-%>' \
-   --changed-group-format='%df%(f=l?:,%dl)c%dF%(F=L?:,%dL)
-%<---
-%>' \
-   --unchanged-group-format='' \
-   old new
-@end example
-
-@node Detailed If-then-else, Example If-then-else, Line Formats, If-then-else
-@subsection Detailed Description of If-then-else Format
-
-For lines common to both files, @code{diff} uses the unchanged line
-group format.  For each hunk of differences in the merged output
-format, if the hunk contains only lines from the first file,
-@code{diff} uses the old line group format; if the hunk contains only
-lines from the second file, @code{diff} uses the new group format;
-otherwise, @code{diff} uses the changed group format.
-
-The old, new, and unchanged line formats specify the output format of
-lines from the first file, lines from the second file, and lines common
-to both files, respectively.
-
-The option @samp{--ifdef=@var{name}} is equivalent to
-the following sequence of options using shell syntax:
-
-@example
---old-group-format='#ifndef @var{name}
-%<#endif /* not @var{name} */
-' \
---new-group-format='#ifdef @var{name}
-%>#endif /* @var{name} */
-' \
---unchanged-group-format='%=' \
---changed-group-format='#ifndef @var{name}
-%<#else /* @var{name} */
-%>#endif /* @var{name} */
-'
-@end example
-
-You should carefully check the @code{diff} output for proper nesting.
-For example, when using the the @samp{-D @var{name}} or
-@samp{--ifdef=@var{name}} option, you should check that if the
-differing lines contain any of the C preprocessor directives
-@samp{#ifdef}, @samp{#ifndef}, @samp{#else}, @samp{#elif}, or
-@samp{#endif}, they are nested properly and match.  If they don't, you
-must make corrections manually.  It is a good idea to carefully check
-the resulting code anyway to make sure that it really does what you
-want it to; depending on how the input files were produced, the output
-might contain duplicate or otherwise incorrect code.
-
-The @code{patch} @samp{-D @var{name}} option behaves just like
-the @code{diff} @samp{-D @var{name}} option, except it operates on
-a file and a diff to produce a merged file; @xref{patch Options}.
-
-@node Example If-then-else, , Detailed If-then-else, If-then-else
-@subsection An Example of If-then-else Format
-
-Here is the output of @samp{diff -DTWO lao tzu} (@pxref{Sample
-diff Input}, for the complete contents of the two files):
-
-@example
-#ifndef TWO
-The Way that can be told of is not the eternal Way;
-The name that can be named is not the eternal name.
-#endif /* not TWO */
-The Nameless is the origin of Heaven and Earth;
-#ifndef TWO
-The Named is the mother of all things.
-#else /* TWO */
-The named is the mother of all things.
-
-#endif /* TWO */
-Therefore let there always be non-being,
-  so we may see their subtlety,
-And let there always be being,
-  so we may see their outcome.
-The two are the same,
-But after they are produced,
-  they have different names.
-#ifdef TWO
-They both may be called deep and profound.
-Deeper and more profound,
-The door of all subtleties!
-#endif /* TWO */
-@end example
-
-@node Comparing Directories, Adjusting Output, Output Formats, Top
-@chapter Comparing Directories
-
-You can use @code{diff} to compare some or all of the files in two
-directory trees.  When both file name arguments to @code{diff} are
-directories, it compares each file that is contained in both
-directories, examining file names in alphabetical order.  Normally
-@code{diff} is silent about pairs of files that contain no differences,
-but if you use the @samp{-s} or @samp{--report-identical-files} option,
-it reports pairs of identical files.  Normally @code{diff} reports
-subdirectories common to both directories without comparing
-subdirectories' files, but if you use the @samp{-r} or
-@samp{--recursive} option, it compares every corresponding pair of files
-in the directory trees, as many levels deep as they go.
-
-For file names that are in only one of the directories, @code{diff}
-normally does not show the contents of the file that exists; it reports
-only that the file exists in that directory and not in the other.  You
-can make @code{diff} act as though the file existed but was empty in the
-other directory, so that it outputs the entire contents of the file that
-actually exists.  (It is output as either an insertion or a
-deletion, depending on whether it is in the first or the second
-directory given.)  To do this, use the @samp{-N} or @samp{--new-file}
-option.
-
-If the older directory contains one or more large files that are not in
-the newer directory, you can make the patch smaller by using the
-@samp{-P} or @samp{--unidirectional-new-file} option instead of @samp{-N}.
-This option is like @samp{-N} except that it only inserts the contents
-of files that appear in the second directory but not the first (that is,
-files that were added).  At the top of the patch, write instructions for
-the user applying the patch to remove the files that were deleted before
-applying the patch.  @xref{Making Patches}, for more discussion of
-making patches for distribution.
-
-To ignore some files while comparing directories, use the @samp{-x
-@var{pattern}} or @samp{--exclude=@var{pattern}} option.  This option
-ignores any files or subdirectories whose base names match the shell
-pattern @var{pattern}.  Unlike in the shell, a period at the start of
-the base of a file name matches a wildcard at the start of a pattern.
-You should enclose @var{pattern} in quotes so that the shell does not
-expand it.  For example, the option @samp{-x '*.[ao]'} ignores any file
-whose name ends with @samp{.a} or @samp{.o}.
-
-This option accumulates if you specify it more than once.  For example,
-using the options @samp{-x 'RCS' -x '*,v'} ignores any file or
-subdirectory whose base name is @samp{RCS} or ends with @samp{,v}.
-
-If you need to give this option many times, you can instead put the
-patterns in a file, one pattern per line, and use the @samp{-X
-@var{file}} or @samp{--exclude-from=@var{file}} option.
-
-If you have been comparing two directories and stopped partway through,
-later you might want to continue where you left off.  You can do this by
-using the @samp{-S @var{file}} or @samp{--starting-file=@var{file}}
-option.  This compares only the file @var{file} and all alphabetically
-later files in the topmost directory level.
-
-@node Adjusting Output, diff Performance, Comparing Directories, Top
-@chapter Making @code{diff} Output Prettier
-
-@code{diff} provides several ways to adjust the appearance of its output.
-These adjustments can be applied to any output format.
-
-@menu
-* Tabs::		Preserving the alignment of tabstops.
-* Pagination::		Page numbering and timestamping @code{diff} output.
-@end menu
-
-@node Tabs, Pagination, , Adjusting Output
-@section Preserving Tabstop Alignment
-@cindex tabstop alignment
-@cindex aligning tabstops
-
-The lines of text in some of the @code{diff} output formats are preceded
-by one or two characters that indicate whether the text is inserted,
-deleted, or changed.  The addition of those characters can cause tabs to
-move to the next tabstop, throwing off the alignment of columns in the
-line.  GNU @code{diff} provides two ways to make tab-aligned columns
-line up correctly.
-
-The first way is to have @code{diff} convert all tabs into the correct
-number of spaces before outputting them; select this method with the
-@samp{-t} or @samp{--expand-tabs} option.  @code{diff} assumes that
-tabstops are set every 8 columns.  To use this form of output with
-@code{patch}, you must give @code{patch} the @samp{-l} or
-@samp{--ignore-white-space} option (@pxref{Changed White Space}, for more
-information).
-
-The other method for making tabs line up correctly is to add a tab
-character instead of a space after the indicator character at the
-beginning of the line.  This ensures that all following tab characters
-are in the same position relative to tabstops that they were in the
-original files, so that the output is aligned correctly.  Its
-disadvantage is that it can make long lines too long to fit on one line
-of the screen or the paper.  It also does not work with the unified
-output format, which does not have a space character after the change
-type indicator character.  Select this method with the @samp{-T} or
-@samp{--initial-tab} option.
-
-@node Pagination, , Tabs, Adjusting Output
-@section Paginating @code{diff} Output
-@cindex paginating @code{diff} output
-
-It can be convenient to have long output page-numbered and time-stamped.
-The @samp{-l} and @samp{--paginate} options do this by sending the
-@code{diff} output through the @code{pr} program.  Here is what the page
-header might look like for @samp{diff -lc lao tzu}:
-
-@example
-Mar 11 13:37 1991  diff -lc lao tzu Page 1
-@end example
-
-@node diff Performance, Comparing Three Files, Adjusting Output, Top
-@chapter @code{diff} Performance Tradeoffs
-@cindex performance of @code{diff}
-
-GNU @code{diff} runs quite efficiently; however, in some circumstances
-you can cause it to run faster or produce a more compact set of changes.
-There are two ways that you can affect the performance of GNU
-@code{diff} by changing the way it compares files.
-
-Performance has more than one dimension.  These options improve one
-aspect of performance at the cost of another, or they improve
-performance in some cases while hurting it in others.
-
-The way that GNU @code{diff} determines which lines have changed always
-comes up with a near-minimal set of differences.  Usually it is good
-enough for practical purposes.  If the @code{diff} output is large, you
-might want @code{diff} to use a modified algorithm that sometimes
-produces a smaller set of differences.  The @samp{-d} or
-@samp{--minimal} option does this; however, it can also cause
-@code{diff} to run more slowly than usual, so it is not the default
-behavior.
-
-When the files you are comparing are large and have small groups of
-changes scattered throughout them, you can use the @samp{-H} or
-@samp{--speed-large-files} option to make a different modification to
-the algorithm that @code{diff} uses.  If the input files have a constant
-small density of changes, this option speeds up the comparisons without
-changing the output.  If not, @code{diff} might produce a larger set of
-differences; however, the output will still be correct.
-
-Normally @code{diff} discards the prefix and suffix that is common to
-both files before it attempts to find a minimal set of differences.
-This makes @code{diff} run faster, but occasionally it may produce
-non-minimal output.  The @samp{--horizon-lines=@var{lines}} option
-prevents @code{diff} from discarding the last @var{lines} lines of the
-prefix and the first @var{lines} lines of the suffix.  This gives
-@code{diff} further opportunities to find a minimal output.
-
-@node Comparing Three Files, diff3 Merging, diff Performance, Top
-@chapter Comparing Three Files
-@cindex comparing three files
-@cindex format of @code{diff3} output
-
-Use the program @code{diff3} to compare three files and show any
-differences among them.  (@code{diff3} can also merge files; see
-@ref{diff3 Merging}).
-
-The ``normal'' @code{diff3} output format shows each hunk of
-differences without surrounding context.  Hunks are labeled depending
-on whether they are two-way or three-way, and lines are annotated by
-their location in the input files.
-
-@xref{Invoking diff3}, for more information on how to run @code{diff3}.
-
-@menu
-* Sample diff3 Input::		Sample @code{diff3} input for examples.
-* Detailed diff3 Normal::	A detailed description of normal output format.
-* diff3 Hunks::			The format of normal output format.
-* Example diff3 Normal::	Sample output in the normal format.
-@end menu
-
-@node Sample diff3 Input, Detailed diff3 Normal, , Comparing Three Files
-@section A Third Sample Input File
-@cindex @code{diff3} sample input
-@cindex sample input for @code{diff3}
-
-Here is a third sample file that will be used in examples to illustrate
-the output of @code{diff3} and how various options can change it.  The
-first two files are the same that we used for @code{diff} (@pxref{Sample
-diff Input}).  This is the third sample file, called @file{tao}:
-
-@example
-The Way that can be told of is not the eternal Way;
-The name that can be named is not the eternal name.
-The Nameless is the origin of Heaven and Earth;
-The named is the mother of all things.
-
-Therefore let there always be non-being,
-  so we may see their subtlety,
-And let there always be being,
-  so we may see their result.
-The two are the same,
-But after they are produced,
-  they have different names.
-
-  -- The Way of Lao-Tzu, tr. Wing-tsit Chan
-@end example
-
-@node Detailed diff3 Normal, diff3 Hunks, Sample diff3 Input, Comparing Three Files
-@section Detailed Description of @code{diff3} Normal Format
-
-Each hunk begins with a line marked @samp{====}.  Three-way hunks have
-plain @samp{====} lines, and two-way hunks have @samp{1}, @samp{2}, or
-@samp{3} appended to specify which of the three input files differ in
-that hunk.  The hunks contain copies of two or three sets of input
-lines each preceded by one or two commands identifying where the lines
-came from.
-
-Normally, two spaces precede each copy of an input line to distinguish
-it from the commands.  But with the @samp{-T} or @samp{--initial-tab}
-option, @code{diff3} uses a tab instead of two spaces; this lines up
-tabs correctly.  @xref{Tabs}, for more information.
-
-Commands take the following forms:
-
-@table @samp
-@item @var{file}:@var{l}a
-This hunk appears after line @var{l} of file @var{file}, and
-contains no lines in that file.  To edit this file to yield the other
-files, one must append hunk lines taken from the other files.  For
-example, @samp{1:11a} means that the hunk follows line 11 in the first
-file and contains no lines from that file.
-
-@item @var{file}:@var{r}c
-This hunk contains the lines in the range @var{r} of file @var{file}.
-The range @var{r} is a comma-separated pair of line numbers, or just one
-number if the range is a singleton.  To edit this file to yield the
-other files, one must change the specified lines to be the lines taken
-from the other files.  For example, @samp{2:11,13c} means that the hunk
-contains lines 11 through 13 from the second file.
-@end table
-
-If the last line in a set of input lines is incomplete
-(@pxref{Incomplete Lines}), it is distinguished on output from a full
-line by a following line that starts with @samp{\}.
-
-@node diff3 Hunks, Example diff3 Normal, Detailed diff3 Normal, Comparing Three Files
-@section @code{diff3} Hunks
-@cindex hunks for @code{diff3}
-@cindex @code{diff3} hunks
-
-Groups of lines that differ in two or three of the input files are
-called @dfn{diff3 hunks}, by analogy with @code{diff} hunks
-(@pxref{Hunks}).  If all three input files differ in a @code{diff3}
-hunk, the hunk is called a @dfn{three-way hunk}; if just two input files
-differ, it is a @dfn{two-way hunk}.
-
-As with @code{diff}, several solutions are possible.  When comparing the
-files @samp{A}, @samp{B}, and @samp{C}, @code{diff3} normally finds
-@code{diff3} hunks by merging the two-way hunks output by the two
-commands @samp{diff A B} and @samp{diff A C}.  This does not necessarily
-minimize the size of the output, but exceptions should be rare.
-
-For example, suppose @file{F} contains the three lines @samp{a},
-@samp{b}, @samp{f}, @file{G} contains the lines @samp{g}, @samp{b},
-@samp{g}, and @file{H} contains the lines @samp{a}, @samp{b},
-@samp{h}.  @samp{diff3 F G H} might output the following:
-
-@example
-====2
-1:1c
-3:1c
-  a
-2:1c
-  g
-====
-1:3c
-  f
-2:3c
-  g
-3:3c
-  h
-@end example
-
-@noindent
-because it found a two-way hunk containing @samp{a} in the first and
-third files and @samp{g} in the second file, then the single line
-@samp{b} common to all three files, then a three-way hunk containing
-the last line of each file.
-
-@node Example diff3 Normal, , diff3 Hunks, Comparing Three Files
-@section An Example of @code{diff3} Normal Format
-
-Here is the output of the command @samp{diff3 lao tzu tao}
-(@pxref{Sample diff3 Input}, for the complete contents of the files).
-Notice that it shows only the lines that are different among the three
-files.
-
-@example
-====2
-1:1,2c
-3:1,2c
-  The Way that can be told of is not the eternal Way;
-  The name that can be named is not the eternal name.
-2:0a
-====1
-1:4c
-  The Named is the mother of all things.
-2:2,3c
-3:4,5c
-  The named is the mother of all things.
-  
-====3
-1:8c
-2:7c
-    so we may see their outcome.
-3:9c
-    so we may see their result.
-====
-1:11a
-2:11,13c
-  They both may be called deep and profound.
-  Deeper and more profound,
-  The door of all subtleties!
-3:13,14c
-  
-    -- The Way of Lao-Tzu, tr. Wing-tsit Chan
-@end example
-
-@node diff3 Merging, Interactive Merging, Comparing Three Files, Top
-@chapter Merging From a Common Ancestor
-@cindex merging from a common ancestor
-
-When two people have made changes to copies of the same file,
-@code{diff3} can produce a merged output that contains both sets of
-changes together with warnings about conflicts.
-
-One might imagine programs with names like @code{diff4} and @code{diff5}
-to compare more than three files simultaneously, but in practice the
-need rarely arises.  You can use @code{diff3} to merge three or more
-sets of changes to a file by merging two change sets at a time.
-
-@code{diff3} can incorporate changes from two modified versions into a
-common preceding version.  This lets you merge the sets of changes
-represented by the two newer files.  Specify the common ancestor version
-as the second argument and the two newer versions as the first and third
-arguments, like this:
-
-@example
-diff3 @var{mine} @var{older} @var{yours}
-@end example
-
-@noindent
-You can remember the order of the arguments by noting that they are in
-alphabetical order.
-
-@cindex conflict
-@cindex overlap
-You can think of this as subtracting @var{older} from @var{yours} and
-adding the result to @var{mine}, or as merging into @var{mine} the
-changes that would turn @var{older} into @var{yours}.  This merging is
-well-defined as long as @var{mine} and @var{older} match in the
-neighborhood of each such change.  This fails to be true when all three
-input files differ or when only @var{older} differs; we call this
-a @dfn{conflict}.  When all three input files differ, we call the
-conflict an @dfn{overlap}.
-
-@code{diff3} gives you several ways to handle overlaps and conflicts.
-You can omit overlaps or conflicts, or select only overlaps,
-or mark conflicts with special @samp{<<<<<<<} and @samp{>>>>>>>} lines.
-
-@code{diff3} can output the merge results as an @code{ed} script that
-that can be applied to the first file to yield the merged output.
-However, it is usually better to have @code{diff3} generate the merged
-output directly; this bypasses some problems with @code{ed}.
-
-@menu
-* Which Changes::		Selecting changes to incorporate.
-* Marking Conflicts::		Marking conflicts.
-* Bypassing ed::		Generating merged output directly.
-* Merging Incomplete Lines::	How @code{diff3} merges incomplete lines.
-* Saving the Changed File::	Emulating System V behavior.
-@end menu
-
-@node Which Changes, Marking Conflicts, , diff3 Merging
-@section Selecting Which Changes to Incorporate
-@cindex overlapping change, selection of
-@cindex unmerged change
-
-You can select all unmerged changes from @var{older} to @var{yours} for merging
-into @var{mine} with the @samp{-e} or @samp{--ed} option.  You can
-select only the nonoverlapping unmerged changes with @samp{-3} or
-@samp{--easy-only}, and you can select only the overlapping changes with
-@samp{-x} or @samp{--overlap-only}.
-
-The @samp{-e}, @samp{-3} and @samp{-x} options select only
-@dfn{unmerged changes}, i.e.@: changes where @var{mine} and @var{yours}
-differ; they ignore changes from @var{older} to @var{yours} where
-@var{mine} and @var{yours} are identical, because they assume that such
-changes have already been merged.  If this assumption is not a safe
-one, you can use the @samp{-A} or @samp{--show-all} option
-(@pxref{Marking Conflicts}).
-
-Here is the output of the command @code{diff3} with each of these three
-options (@pxref{Sample diff3 Input}, for the complete contents of the files).
-Notice that @samp{-e} outputs the union of the disjoint sets of changes
-output by @samp{-3} and @samp{-x}.
-
-Output of @samp{diff3 -e lao tzu tao}:
-@example
-11a
-
-  -- The Way of Lao-Tzu, tr. Wing-tsit Chan
-.
-8c
-  so we may see their result.
-.
-@end example
-
-Output of @samp{diff3 -3 lao tzu tao}:
-@example
-8c
-  so we may see their result.
-.
-@end example
-
-Output of @samp{diff3 -x lao tzu tao}:
-@example
-11a
-
-  -- The Way of Lao-Tzu, tr. Wing-tsit Chan
-.
-@end example
-
-@node Marking Conflicts, Bypassing ed, Which Changes, diff3 Merging
-@section Marking Conflicts
-@cindex conflict marking
-@cindex @samp{<<<<<<<} for marking conflicts
-
-@code{diff3} can mark conflicts in the merged output by
-bracketing them with special marker lines.  A conflict
-that comes from two files @var{A} and @var{B} is marked as follows:
-
-@example
-<<<<<<< @var{A}
-@r{lines from @var{A}}
-=======
-@r{lines from @var{B}}
->>>>>>> @var{B}
-@end example
-
-A conflict that comes from three files @var{A}, @var{B} and @var{C} is
-marked as follows:
-
-@example
-<<<<<<< @var{A}
-@r{lines from @var{A}}
-||||||| @var{B}
-@r{lines from @var{B}}
-=======
-@r{lines from @var{C}}
->>>>>>> @var{C}
-@end example
-
-The @samp{-A} or @samp{--show-all} option acts like the @samp{-e}
-option, except that it brackets conflicts, and it outputs all changes
-from @var{older} to @var{yours}, not just the unmerged changes.  Thus,
-given the sample input files (@pxref{Sample diff3 Input}), @samp{diff3
--A lao tzu tao} puts brackets around the conflict where only @file{tzu}
-differs:
-
-@example
-<<<<<<< tzu
-=======
-The Way that can be told of is not the eternal Way;
-The name that can be named is not the eternal name.
->>>>>>> tao
-@end example
-
-And it outputs the three-way conflict as follows:
-
-@example
-<<<<<<< lao
-||||||| tzu
-They both may be called deep and profound.
-Deeper and more profound,
-The door of all subtleties!
-=======
-
-  -- The Way of Lao-Tzu, tr. Wing-tsit Chan
->>>>>>> tao
-@end example
-
-The @samp{-E} or @samp{--show-overlap} option outputs less information
-than the @samp{-A} or @samp{--show-all} option, because it outputs only
-unmerged changes, and it never outputs the contents of the second
-file.  Thus the @samp{-E} option acts like the @samp{-e} option,
-except that it brackets the first and third files from three-way
-overlapping changes.  Similarly, @samp{-X} acts like @samp{-x}, except
-it brackets all its (necessarily overlapping) changes.  For example,
-for the three-way overlapping change above, the @samp{-E} and @samp{-X}
-options output the following:
-
-@example
-<<<<<<< lao
-=======
-
-  -- The Way of Lao-Tzu, tr. Wing-tsit Chan
->>>>>>> tao
-@end example
-
-If you are comparing files that have meaningless or uninformative names,
-you can use the @samp{-L @var{label}} or @samp{--label=@var{label}}
-option to show alternate names in the @samp{<<<<<<<}, @samp{|||||||}
-and @samp{>>>>>>>} brackets.  This option can be given up to three
-times, once for each input file.  Thus @samp{diff3 -A -L X -L Y -L Z A
-B C} acts like @samp{diff3 -A A B C}, except that the output looks like
-it came from files named @samp{X}, @samp{Y} and @samp{Z} rather than
-from files named @samp{A}, @samp{B} and @samp{C}.
-
-@node Bypassing ed, Merging Incomplete Lines, Marking Conflicts, diff3 Merging
-@section Generating the Merged Output Directly
-@cindex merged @code{diff3} format
-
-With the @samp{-m} or @samp{--merge} option, @code{diff3} outputs the
-merged file directly.  This is more efficient than using @code{ed} to
-generate it, and works even with non-text files that @code{ed} would
-reject.  If you specify @samp{-m} without an @code{ed} script option,
-@samp{-A} (@samp{--show-all}) is assumed.
-
-For example, the command @samp{diff3 -m lao tzu tao}
-(@pxref{Sample diff3 Input} for a copy of the input files) would output
-the following:
-
-@example
-<<<<<<< tzu
-=======
-The Way that can be told of is not the eternal Way;
-The name that can be named is not the eternal name.
->>>>>>> tao
-The Nameless is the origin of Heaven and Earth;
-The Named is the mother of all things.
-Therefore let there always be non-being,
-  so we may see their subtlety,
-And let there always be being,
-  so we may see their result.
-The two are the same,
-But after they are produced,
-  they have different names.
-<<<<<<< lao
-||||||| tzu
-They both may be called deep and profound.
-Deeper and more profound,
-The door of all subtleties!
-=======
-
-  -- The Way of Lao-Tzu, tr. Wing-tsit Chan
->>>>>>> tao
-@end example
-
-@node Merging Incomplete Lines, Saving the Changed File, Bypassing ed, diff3 Merging
-@section How @code{diff3} Merges Incomplete Lines
-@cindex incomplete line merging
-
-With @samp{-m}, incomplete lines (@pxref{Incomplete Lines}) are simply
-copied to the output as they are found; if the merged output ends in an
-conflict and one of the input files ends in an incomplete
-line, succeeding @samp{|||||||}, @samp{=======} or @samp{>>>>>>>}
-brackets appear somewhere other than the start of a line because
-they are appended to the incomplete line.
-
-Without @samp{-m}, if an @code{ed} script option is specified and an
-incomplete line is found, @code{diff3} generates a warning and acts as
-if a newline had been present.
-
-@node Saving the Changed File, , Merging Incomplete Lines, diff3 Merging
-@section Saving the Changed File
-@cindex System V @code{diff3} compatibility
-
-Traditional Unix @code{diff3} generates an @code{ed} script without the
-trailing @samp{w} and and @samp{q} commands that save the changes.
-System V @code{diff3} generates these extra commands.  GNU @code{diff3}
-normally behaves like traditional Unix @code{diff3}, but with the
-@samp{-i} option it behaves like System V @code{diff3} and appends the
-@samp{w} and @samp{q} commands.
-
-The @samp{-i} option requires one of the @code{ed} script options
-@samp{-AeExX3}, and is incompatible with the merged output option
-@samp{-m}.
-
-@node Interactive Merging, Merging with patch, diff3 Merging, Top
-@chapter Interactive Merging with @code{sdiff}
-@cindex diff merging
-@cindex interactive merging
-
-With @code{sdiff}, you can merge two files interactively based on a
-side-by-side @samp{-y} format comparison (@pxref{Side by Side}).  Use
-@samp{-o @var{file}} or @samp{--output=@var{file}} to specify where to
-put the merged text.  @xref{Invoking sdiff}, for more details on the
-options to @code{sdiff}.
-
-Another way to merge files interactively is to use the Emacs Lisp
-package @code{emerge}.  @xref{emerge, , emerge, emacs, The GNU Emacs
-Manual}, for more information.
-
-@menu
-* sdiff Option Summary::Summary of @code{sdiff} options.
-* Merge Commands::	Merging two files interactively.
-@end menu
-
-@node sdiff Option Summary, Merge Commands, , Interactive Merging
-@section Specifying @code{diff} Options to @code{sdiff}
-@cindex @code{sdiff} output format
-
-The following @code{sdiff} options have the same meaning as for
-@code{diff}.  @xref{diff Options}, for the use of these options.
-
-@example
--a -b -d -i -t -v
--B -H -I @var{regexp}
-
---ignore-blank-lines  --ignore-case
---ignore-matching-lines=@var{regexp}  --ignore-space-change
---left-column  --minimal  --speed-large-files
---suppress-common-lines  --expand-tabs
---text  --version  --width=@var{columns}
-@end example
-
-For historical reasons, @code{sdiff} has alternate names for some
-options.  The @samp{-l} option is equivalent to the @samp{--left-column}
-option, and similarly @samp{-s} is equivalent to
-@samp{--suppress-common-lines}.  The meaning of the @code{sdiff}
-@samp{-w} and @samp{-W} options is interchanged from that of
-@code{diff}: with @code{sdiff}, @samp{-w @var{columns}} is equivalent to
-@samp{--width=@var{columns}}, and @samp{-W} is equivalent to
-@samp{--ignore-all-space}.  @code{sdiff} without the @samp{-o} option is
-equivalent to @code{diff} with the @samp{-y} or @samp{--side-by-side}
-option (@pxref{Side by Side}).
-
-@node Merge Commands, , sdiff Option Summary, Interactive Merging
-@section Merge Commands
-@cindex merge commands
-@cindex merging interactively
-
-Groups of common lines, with a blank gutter, are copied from the first
-file to the output.  After each group of differing lines, @code{sdiff}
-prompts with @samp{%} and pauses, waiting for one of the following
-commands.  Follow each command with @key{RET}.
-
-@table @samp
-@item e
-Discard both versions.
-Invoke a text editor on an empty temporary file,
-then copy the resulting file to the output.
-
-@item eb
-Concatenate the two versions, edit the result in a temporary file,
-then copy the edited result to the output.
-
-@item el
-Edit a copy of the left version, then copy the result to the output.
-
-@item er
-Edit a copy of the right version, then copy the result to the output.
-
-@item l
-Copy the left version to the output.
-
-@item q
-Quit.
-
-@item r
-Copy the right version to the output.
-
-@item s
-Silently copy common lines.
-
-@item v
-Verbosely copy common lines.  This is the default.
-@end table
-
-The text editor invoked is specified by the @code{EDITOR} environment
-variable if it is set.  The default is system-dependent.
-
-@node Merging with patch, Making Patches, Interactive Merging, Top
-@chapter Merging with @code{patch}
-
-@code{patch} takes comparison output produced by @code{diff} and applies
-the differences to a copy of the original file, producing a patched
-version.  With @code{patch}, you can distribute just the changes to a
-set of files instead of distributing the entire file set; your
-correspondents can apply @code{patch} to update their copy of the files
-with your changes.  @code{patch} automatically determines the diff
-format, skips any leading or trailing headers, and uses the headers to
-determine which file to patch.  This lets your correspondents feed an
-article or message containing a difference listing directly to
-@code{patch}.
-
-@code{patch} detects and warns about common problems like forward
-patches.  It saves the original version of the files it patches, and
-saves any patches that it could not apply.  It can also maintain a
-@code{patchlevel.h} file to ensures that your correspondents apply
-diffs in the proper order.
-
-@code{patch} accepts a series of diffs in its standard input, usually
-separated by headers that specify which file to patch.  It applies
-@code{diff} hunks (@pxref{Hunks}) one by one.  If a hunk does not
-exactly match the original file, @code{patch} uses heuristics to try to
-patch the file as well as it can.  If no approximate match can be found,
-@code{patch} rejects the hunk and skips to the next hunk.  @code{patch}
-normally replaces each file @var{f} with its new version, saving the
-original file in @samp{@var{f}.orig}, and putting reject hunks (if any)
-into @samp{@var{f}.rej}.
-
-@xref{Invoking patch}, for detailed information on the options to
-@code{patch}.  @xref{Backups}, for more information on how
-@code{patch} names backup files.  @xref{Rejects}, for more information
-on where @code{patch} puts reject hunks.
-
-@menu
-* patch Input::		Selecting the type of @code{patch} input.
-* Imperfect::		Dealing with imperfect patches.
-* Empty Files::		Removing empty files after patching.
-* Multiple Patches::	Handling multiple patches in a file specially.
-* patch Messages::	Messages and questions @code{patch} can produce.
-@end menu
-
-@node patch Input, Imperfect, , Merging with patch
-@section Selecting the @code{patch} Input Format
-@cindex @code{patch} input format
-
-@code{patch} normally determines which @code{diff} format the patch
-file uses by examining its contents.  For patch files that contain
-particularly confusing leading text, you might need to use one of the
-following options to force @code{patch} to interpret the patch file as a
-certain format of diff.  The output formats listed here are the only
-ones that @code{patch} can understand.
-
-@table @samp
-@item -c
-@itemx --context
-context diff.
-
-@item -e
-@itemx --ed
-@code{ed} script.
-
-@item -n
-@itemx --normal
-normal diff.
-
-@item -u
-@itemx --unified
-unified diff.
-@end table
-
-@node Imperfect, Empty Files, patch Input, Merging with patch
-@section Applying Imperfect Patches
-@cindex imperfect patch application
-
-@code{patch} tries to skip any leading text in the patch file, apply the
-diff, and then skip any trailing text.  Thus you can feed a news article
-or mail message directly to @code{patch}, and it should work.  If the
-entire diff is indented by a constant amount of white space, @code{patch}
-automatically ignores the indentation.
-
-However, certain other types of imperfect input require user
-intervention.
-
-@menu
-* Changed White Space::	When tabs and spaces don't match exactly.
-* Reversed Patches::	Applying reversed patches correctly.
-* Inexact::		Helping @code{patch} find close matches.
-@end menu
-
-@node Changed White Space, Reversed Patches, , Imperfect
-@subsection Applying Patches with Changed White Space
-@cindex white space in patches
-
-Sometimes mailers, editors, or other programs change spaces into tabs,
-or vice versa.  If this happens to a patch file or an input file, the
-files might look the same, but @code{patch} will not be able to match
-them properly.  If this problem occurs, use the @samp{-l} or
-@samp{--ignore-white-space} option, which makes @code{patch} compare
-white space loosely so that any sequence of white space in the patch file
-matches any sequence of white space in the input files.  Non-white-space
-characters must still match exactly.  Each line of the context must
-still match a line in the input file.
-
-@node Reversed Patches, Inexact, Changed White Space, Imperfect
-@subsection Applying Reversed Patches
-@cindex reversed patches
-
-Sometimes people run @code{diff} with the new file first instead of
-second.  This creates a diff that is ``reversed''.  To apply such
-patches, give @code{patch} the @samp{-R} or @samp{--reverse} option.
-@code{patch} then attempts to swap each hunk around before applying it.
-Rejects come out in the swapped format.  The @samp{-R} option does not
-work with @code{ed} scripts because there is too little information in
-them to reconstruct the reverse operation.
-
-Often @code{patch} can guess that the patch is reversed.  If the first
-hunk of a patch fails, @code{patch} reverses the hunk to see if it can
-apply it that way.  If it can, @code{patch} asks you if you want to have
-the @samp{-R} option set; if it can't, @code{patch} continues to apply
-the patch normally.  This method cannot detect a reversed patch if it is
-a normal diff and the first command is an append (which should have been
-a delete) since appends always succeed, because a null context matches
-anywhere.  But most patches add or change lines rather than delete them,
-so most reversed normal diffs begin with a delete, which fails, and
-@code{patch} notices.
-
-If you apply a patch that you have already applied, @code{patch} thinks
-it is a reversed patch and offers to un-apply the patch.  This could be
-construed as a feature.  If you did this inadvertently and you don't
-want to un-apply the patch, just answer @samp{n} to this offer and to
-the subsequent ``apply anyway'' question---or type @kbd{C-c} to kill the
-@code{patch} process.
-
-@node Inexact, , Reversed Patches, Imperfect
-@subsection Helping @code{patch} Find Inexact Matches
-@cindex inexact patches
-@cindex fuzz factor when patching
-
-For context diffs, and to a lesser extent normal diffs, @code{patch} can
-detect when the line numbers mentioned in the patch are incorrect, and
-it attempts to find the correct place to apply each hunk of the patch.
-As a first guess, it takes the line number mentioned in the hunk, plus
-or minus any offset used in applying the previous hunk.  If that is not
-the correct place, @code{patch} scans both forward and backward for a
-set of lines matching the context given in the hunk.
-
-First @code{patch} looks for a place where all lines of the context
-match.  If it cannot find such a place, and it is reading a context or
-unified diff, and the maximum fuzz factor is set to 1 or more, then
-@code{patch} makes another scan, ignoring the first and last line of
-context.  If that fails, and the maximum fuzz factor is set to 2 or
-more, it makes another scan, ignoring the first two and last two lines
-of context are ignored.  It continues similarly if the maximum fuzz
-factor is larger.
-
-The @samp{-F @var{lines}} or @samp{--fuzz=@var{lines}} option sets the
-maximum fuzz factor to @var{lines}.  This option only applies to context
-and unified diffs; it ignores up to @var{lines} lines while looking for
-the place to install a hunk.  Note that a larger fuzz factor increases
-the odds of making a faulty patch.  The default fuzz factor is 2; it may
-not be set to more than the number of lines of context in the diff,
-ordinarily 3.
-
-If @code{patch} cannot find a place to install a hunk of the patch, it
-writes the hunk out to a reject file (@pxref{Rejects}, for information
-on how reject files are named).  It writes out rejected hunks in context
-format no matter what form the input patch is in.  If the input is a
-normal or @code{ed} diff, many of the contexts are simply null.  The
-line numbers on the hunks in the reject file may be different from those
-in the patch file: they show the approximate location where @code{patch}
-thinks the failed hunks belong in the new file rather than in the old
-one.
-
-As it completes each hunk, @code{patch} tells you whether the hunk
-succeeded or failed, and if it failed, on which line (in the new file)
-@code{patch} thinks the hunk should go.  If this is different from the
-line number specified in the diff, it tells you the offset.  A single
-large offset @emph{may} indicate that @code{patch} installed a hunk in
-the wrong place.  @code{patch} also tells you if it used a fuzz factor
-to make the match, in which case you should also be slightly suspicious.
-
-@code{patch} cannot tell if the line numbers are off in an @code{ed}
-script, and can only detect wrong line numbers in a normal diff when it
-finds a change or delete command.  It may have the same problem with a
-context diff using a fuzz factor equal to or greater than the number of
-lines of context shown in the diff (typically 3).  In these cases, you
-should probably look at a context diff between your original and patched
-input files to see if the changes make sense.  Compiling without errors
-is a pretty good indication that the patch worked, but not a guarantee.
-
-@code{patch} usually produces the correct results, even when it must
-make many guesses.  However, the results are guaranteed only when
-the patch is applied to an exact copy of the file that the patch was
-generated from.
-
-@node Empty Files, Multiple Patches, Imperfect, Merging with patch
-@section Removing Empty Files
-@cindex empty files, removing
-@cindex removing empty files
-
-Sometimes when comparing two directories, the first directory contains a
-file that the second directory does not.  If you give @code{diff} the
-@samp{-N} or @samp{--new-file} option, it outputs a diff that deletes
-the contents of this file.  By default, @code{patch} leaves an empty
-file after applying such a diff.  The @samp{-E} or
-@samp{--remove-empty-files} option to @code{patch} deletes output files
-that are empty after applying the diff.
-
-@node Multiple Patches, patch Messages, Empty Files, Merging with patch
-@section Multiple Patches in a File
-@cindex multiple patches
-
-If the patch file contains more than one patch, @code{patch} tries to
-apply each of them as if they came from separate patch files.  This
-means that it determines the name of the file to patch for each patch,
-and that it examines the leading text before each patch for file names
-and prerequisite revision level (@pxref{Making Patches}, for more on
-that topic).
-
-For the second and subsequent patches in the patch file, you can give
-options and another original file name by separating their argument
-lists with a @samp{+}.  However, the argument list for a second or
-subsequent patch may not specify a new patch file, since that does not
-make sense.
-
-For example, to tell @code{patch} to strip the first three slashes from
-the name of the first patch in the patch file and none from subsequent
-patches, and to use @file{code.c} as the first input file, you can use:
-
-@example
-patch -p3 code.c + -p0 < patchfile
-@end example
-
-The @samp{-S} or @samp{--skip} option ignores the current patch from the
-patch file, but continue looking for the next patch in the file.  Thus,
-to ignore the first and third patches in the patch file, you can use:
-
-@example
-patch -S + + -S + < patch file
-@end example
-
-@node patch Messages, , Multiple Patches, Merging with patch
-@section Messages and Questions from @code{patch}
-@cindex @code{patch} messages and questions
-@cindex diagnostics from @code{patch}
-@cindex messages from @code{patch}
-
-@code{patch} can produce a variety of messages, especially if it has
-trouble decoding its input.  In a few situations where it's not sure how
-to proceed, @code{patch} normally prompts you for more information from
-the keyboard.  There are options to suppress printing non-fatal messages
-and stopping for keyboard input.
-
-The message @samp{Hmm...} indicates that @code{patch} is reading text in
-the patch file, attempting to determine whether there is a patch in that
-text, and if so, what kind of patch it is.
-
-You can inhibit all terminal output from @code{patch}, unless an error
-occurs, by using the @samp{-s}, @samp{--quiet}, or @samp{--silent}
-option.
-
-There are two ways you can prevent @code{patch} from asking you any
-questions.  The @samp{-f} or @samp{--force} option assumes that you know
-what you are doing.  It assumes the following:
-
-@itemize @bullet
-@item
-skip patches that do not contain file names in their headers;
-
-@item
-patch files even though they have the wrong version for the
-@samp{Prereq:} line in the patch;
-
-@item
-assume that patches are not reversed even if they look like they are.
-@end itemize
-
-The @samp{-t} or @samp{--batch} option is similar to @samp{-f}, in that
-it suppresses questions, but it makes somewhat different assumptions:
-
-@itemize @bullet
-@item
-skip patches that do not contain file names in their headers
-(the same as @samp{-f});
-
-@item
-skip patches for which the file has the wrong version for the
-@samp{Prereq:} line in the patch;
-
-@item
-assume that patches are reversed if they look like they are.
-@end itemize
-
-@code{patch} exits with a non-zero status if it creates any reject
-files.  When applying a set of patches in a loop, you should check the
-exit status, so you don't apply a later patch to a partially patched
-file.
-
-@node Making Patches, Invoking cmp, Merging with patch, Top
-@chapter Tips for Making Patch Distributions
-@cindex patch making tips
-@cindex tips for patch making
-
-Here are some things you should keep in mind if you are going to
-distribute patches for updating a software package.
-
-Make sure you have specified the file names correctly, either in a
-context diff header or with an @samp{Index:} line.  If you are patching
-files in a subdirectory, be sure to tell the patch user to specify a
-@samp{-p} or @samp{--strip} option as needed.  Take care to not send out
-reversed patches, since these make people wonder whether they have
-already applied the patch.
-
-To save people from partially applying a patch before other patches that
-should have gone before it, you can make the first patch in the patch
-file update a file with a name like @file{patchlevel.h} or
-@file{version.c}, which contains a patch level or version number.  If
-the input file contains the wrong version number, @code{patch} will
-complain immediately.
-
-An even clearer way to prevent this problem is to put a @samp{Prereq:}
-line before the patch.  If the leading text in the patch file contains a
-line that starts with @samp{Prereq:}, @code{patch} takes the next word
-from that line (normally a version number) and checks whether the next
-input file contains that word, preceded and followed by either
-white space or a newline.  If not, @code{patch} prompts you for
-confirmation before proceeding.  This makes it difficult to accidentally
-apply patches in the wrong order.
-
-Since @code{patch} does not handle incomplete lines properly, make sure
-that all the source files in your program end with a newline whenever
-you release a version.
-
-To create a patch that changes an older version of a package into a
-newer version, first make a copy of the older version in a scratch
-directory.  Typically you do that by unpacking a @code{tar} or
-@code{shar} archive of the older version.
-
-You might be able to reduce the size of the patch by renaming or
-removing some files before making the patch.  If the older version of
-the package contains any files that the newer version does not, or if
-any files have been renamed between the two versions, make a list of
-@code{rm} and @code{mv} commands for the user to execute in the old
-version directory before applying the patch.  Then run those commands
-yourself in the scratch directory.
-
-If there are any files that you don't need to include in the patch
-because they can easily be rebuilt from other files (for example,
-@file{TAGS} and output from @code{yacc} and @code{makeinfo}), replace
-the versions in the scratch directory with the newer versions, using
-@code{rm} and @code{ln} or @code{cp}.
-
-Now you can create the patch.  The de-facto standard @code{diff} format
-for patch distributions is context format with two lines of context,
-produced by giving @code{diff} the @samp{-C 2} option.  Do not use less
-than two lines of context, because @code{patch} typically needs at
-least two lines for proper operation.  Give @code{diff} the @samp{-P}
-option in case the newer version of the package contains any files that
-the older one does not.  Make sure to specify the scratch directory
-first and the newer directory second.
-
-Add to the top of the patch a note telling the user any @code{rm} and
-@code{mv} commands to run before applying the patch.  Then you can
-remove the scratch directory.
-
-@node Invoking cmp, Invoking diff, Making Patches, Top
-@chapter Invoking @code{cmp}
-@cindex invoking @code{cmp}
-@cindex @code{cmp} invocation
-
-The @code{cmp} command compares two files, and if they differ, tells the
-first byte and line number where they differ.  Its arguments are as
-follows:
-
-@example
-cmp @var{options}@dots{} @var{from-file} @r{[}@var{to-file}@var{]}
-@end example
-
-The file name @samp{-} is always the standard input.  @code{cmp} also
-uses the standard input if one file name is omitted.
-
-An exit status of 0 means no differences were found, 1 means some
-differences were found, and 2 means trouble.
-
-@menu
-* cmp Options::		Summary of options to @code{cmp}.
-@end menu
-
-@node cmp Options, , , Invoking cmp
-@section Options to @code{cmp}
-@cindex @code{cmp} options
-@cindex options for @code{cmp}
-
-Below is a summary of all of the options that GNU @code{cmp} accepts.
-Most options have two equivalent names, one of which is a single letter
-preceded by @samp{-}, and the other of which is a long name preceded by
-@samp{--}.  Multiple single letter options (unless they take an
-argument) can be combined into a single command line word: @samp{-cl} is
-equivalent to @samp{-c -l}.
-
-@table @samp
-@item -c
-Print the differing characters.  Display control characters as a
-@samp{^} followed by a letter of the alphabet and precede characters
-that have the high bit set with @samp{M-} (which stands for ``meta'').
-
-@item --ignore-initial=@var{bytes}
-Ignore any differences in the the first @var{bytes} bytes of the input files.
-Treat files with fewer than @var{bytes} bytes as if they are empty.
-
-@item -l
-Print the (decimal) offsets and (octal) values of all differing bytes.
-
-@item --print-chars
-Print the differing characters.  Display control characters as a
-@samp{^} followed by a letter of the alphabet and precede characters
-that have the high bit set with @samp{M-} (which stands for ``meta'').
-
-@item --quiet
-@itemx -s
-@itemx --silent
-Do not print anything; only return an exit status indicating whether
-the files differ.
-
-@item --verbose
-Print the (decimal) offsets and (octal) values of all differing bytes.
-
-@item -v
-@item --version
-Output the version number of @code{cmp}.
-@end table
-
-@node Invoking diff, Invoking diff3, Invoking cmp, Top
-@chapter Invoking @code{diff}
-@cindex invoking @code{diff}
-@cindex @code{diff} invocation
-
-The format for running the @code{diff} command is:
-
-@example
-diff @var{options}@dots{} @var{from-file} @var{to-file}
-@end example
-
-In the simplest case, @code{diff} compares the contents of the two files
-@var{from-file} and @var{to-file}.  A file name of @samp{-} stands for
-text read from the standard input.  As a special case, @samp{diff - -}
-compares a copy of standard input to itself.
-
-If @var{from-file} is a directory and @var{to-file} is not, @code{diff}
-compares the file in @var{from-file} whose file name is that of @var{to-file},
-and vice versa.  The non-directory file must not be @samp{-}.
-
-If both @var{from-file} and @var{to-file} are directories,
-@code{diff} compares corresponding files in both directories, in
-alphabetical order; this comparison is not recursive unless the
-@samp{-r} or @samp{--recursive} option is given.  @code{diff} never
-compares the actual contents of a directory as if it were a file.  The
-file that is fully specified may not be standard input, because standard
-input is nameless and the notion of ``file with the same name'' does not
-apply.
-
-@code{diff} options begin with @samp{-}, so normally @var{from-file} and
-@var{to-file} may not begin with @samp{-}.  However, @samp{--} as an
-argument by itself treats the remaining arguments as file names even if
-they begin with @samp{-}.
-
-An exit status of 0 means no differences were found, 1 means some
-differences were found, and 2 means trouble.
-
-@menu
-* diff Options::	Summary of options to @code{diff}.
-@end menu
-
-@node diff Options, , , Invoking diff
-@section Options to @code{diff}
-@cindex @code{diff} options
-@cindex options for @code{diff}
-
-Below is a summary of all of the options that GNU @code{diff} accepts.
-Most options have two equivalent names, one of which is a single letter
-preceded by @samp{-}, and the other of which is a long name preceded by
-@samp{--}.  Multiple single letter options (unless they take an
-argument) can be combined into a single command line word: @samp{-ac} is
-equivalent to @samp{-a -c}.  Long named options can be abbreviated to
-any unique prefix of their name.  Brackets ([ and ]) indicate that an
-option takes an optional argument.
-
-@table @samp
-@item -@var{lines}
-Show @var{lines} (an integer) lines of context.  This option does not
-specify an output format by itself; it has no effect unless it is
-combined with @samp{-c} (@pxref{Context Format}) or @samp{-u}
-(@pxref{Unified Format}).  This option is obsolete.  For proper
-operation, @code{patch} typically needs at least two lines of context.
-
-@item -a
-Treat all files as text and compare them line-by-line, even if they
-do not seem to be text.  @xref{Binary}.
-
-@item -b
-Ignore changes in amount of white space.  @xref{White Space}.
-
-@item -B
-Ignore changes that just insert or delete blank lines.  @xref{Blank
-Lines}.
-
-@item --binary
-Read and write data in binary mode.  @xref{Binary}.
-
-@item --brief
-Report only whether the files differ, not the details of the
-differences.  @xref{Brief}.
-
-@item -c
-Use the context output format.  @xref{Context Format}.
-
-@item -C @var{lines}
-@itemx --context@r{[}=@var{lines}@r{]}
-Use the context output format, showing @var{lines} (an integer) lines of
-context, or three if @var{lines} is not given.  @xref{Context Format}.
-For proper operation, @code{patch} typically needs at least two lines of
-context.
-
-@item --changed-group-format=@var{format}
-Use @var{format} to output a line group containing differing lines from
-both files in if-then-else format.  @xref{Line Group Formats}.
-
-@item -d
-Change the algorithm perhaps find a smaller set of changes.  This makes
-@code{diff} slower (sometimes much slower).  @xref{diff Performance}.
-
-@item -D @var{name}
-Make merged @samp{#ifdef} format output, conditional on the preprocessor
-macro @var{name}.  @xref{If-then-else}.
-
-@item -e
-@itemx --ed
-Make output that is a valid @code{ed} script.  @xref{ed Scripts}.
-
-@item --exclude=@var{pattern}
-When comparing directories, ignore files and subdirectories whose basenames
-match @var{pattern}.  @xref{Comparing Directories}.
-
-@item --exclude-from=@var{file}
-When comparing directories, ignore files and subdirectories whose basenames
-match any pattern contained in @var{file}.  @xref{Comparing Directories}.
-
-@item --expand-tabs
-Expand tabs to spaces in the output, to preserve the alignment of tabs
-in the input files.  @xref{Tabs}.
-
-@item -f
-Make output that looks vaguely like an @code{ed} script but has changes
-in the order they appear in the file.  @xref{Forward ed}.
-
-@item -F @var{regexp}
-In context and unified format, for each hunk of differences, show some
-of the last preceding line that matches @var{regexp}.  @xref{Specified
-Headings}.
-
-@item --forward-ed
-Make output that looks vaguely like an @code{ed} script but has changes
-in the order they appear in the file.  @xref{Forward ed}.
-
-@item -h
-This option currently has no effect; it is present for Unix
-compatibility.
-
-@item -H
-Use heuristics to speed handling of large files that have numerous
-scattered small changes.  @xref{diff Performance}.
-
-@item --horizon-lines=@var{lines}
-Do not discard the last @var{lines} lines of the common prefix
-and the first @var{lines} lines of the common suffix.
-@xref{diff Performance}.
-
-@item -i
-Ignore changes in case; consider upper- and lower-case letters
-equivalent.  @xref{Case Folding}.
-
-@item -I @var{regexp}
-Ignore changes that just insert or delete lines that match @var{regexp}.
-@xref{Specified Folding}.
-
-@item --ifdef=@var{name}
-Make merged if-then-else output using @var{name}.  @xref{If-then-else}.
-
-@item --ignore-all-space
-Ignore white space when comparing lines.  @xref{White Space}.
-
-@item --ignore-blank-lines
-Ignore changes that just insert or delete blank lines.  @xref{Blank
-Lines}.
-
-@item --ignore-case
-Ignore changes in case; consider upper- and lower-case to be the same.
-@xref{Case Folding}.
-
-@item --ignore-matching-lines=@var{regexp}
-Ignore changes that just insert or delete lines that match @var{regexp}.
-@xref{Specified Folding}.
-
-@item --ignore-space-change
-Ignore changes in amount of white space.
-@xref{White Space}.
-
-@item --initial-tab
-Output a tab rather than a space before the text of a line in normal or
-context format.  This causes the alignment of tabs in the line to look
-normal.  @xref{Tabs}.
-
-@item -l
-Pass the output through @code{pr} to paginate it.  @xref{Pagination}.
-
-@item -L @var{label}
-Use @var{label} instead of the file name in the context format
-(@pxref{Context Format}) and unified format (@pxref{Unified Format})
-headers.  @xref{RCS}.
-
-@item --label=@var{label}
-Use @var{label} instead of the file name in the context format
-(@pxref{Context Format}) and unified format (@pxref{Unified Format})
-headers.
-
-@item --left-column
-Print only the left column of two common lines in side by side format.
-@xref{Side by Side Format}.
-
-@item --line-format=@var{format}
-Use @var{format} to output all input lines in if-then-else format.
-@xref{Line Formats}.
-
-@item --minimal
-Change the algorithm to perhaps find a smaller set of changes.  This
-makes @code{diff} slower (sometimes much slower).  @xref{diff
-Performance}.
-
-@item -n
-Output RCS-format diffs; like @samp{-f} except that each command
-specifies the number of lines affected.  @xref{RCS}.
-
-@item -N
-@itemx --new-file
-In directory comparison, if a file is found in only one directory,
-treat it as present but empty in the other directory.  @xref{Comparing
-Directories}.
-
-@item --new-group-format=@var{format}
-Use @var{format} to output a group of lines taken from just the second
-file in if-then-else format.  @xref{Line Group Formats}.
-
-@item --new-line-format=@var{format}
-Use @var{format} to output a line taken from just the second file in
-if-then-else format.  @xref{Line Formats}.
-
-@item --old-group-format=@var{format}
-Use @var{format} to output a group of lines taken from just the first
-file in if-then-else format.  @xref{Line Group Formats}.
-
-@item --old-line-format=@var{format}
-Use @var{format} to output a line taken from just the first file in
-if-then-else format.  @xref{Line Formats}.
-
-@item -p
-Show which C function each change is in.  @xref{C Function Headings}.
-
-@item -P
-When comparing directories, if a file appears only in the second
-directory of the two, treat it as present but empty in the other.
-@xref{Comparing Directories}.
-
-@item --paginate
-Pass the output through @code{pr} to paginate it.  @xref{Pagination}.
-
-@item -q
-Report only whether the files differ, not the details of the
-differences.  @xref{Brief}.
-
-@item -r
-When comparing directories, recursively compare any subdirectories
-found.  @xref{Comparing Directories}.
-
-@item --rcs
-Output RCS-format diffs; like @samp{-f} except that each command
-specifies the number of lines affected.  @xref{RCS}.
-
-@item --recursive
-When comparing directories, recursively compare any subdirectories
-found.  @xref{Comparing Directories}.
-
-@item --report-identical-files
-Report when two files are the same.  @xref{Comparing Directories}.
-
-@item -s
-Report when two files are the same.  @xref{Comparing Directories}.
-
-@item -S @var{file}
-When comparing directories, start with the file @var{file}.  This is
-used for resuming an aborted comparison.  @xref{Comparing Directories}.
-
-@item --sdiff-merge-assist
-Print extra information to help @code{sdiff}.  @code{sdiff} uses this
-option when it runs @code{diff}.  This option is not intended for users
-to use directly.
-
-@item --show-c-function
-Show which C function each change is in.  @xref{C Function Headings}.
-
-@item --show-function-line=@var{regexp}
-In context and unified format, for each hunk of differences, show some
-of the last preceding line that matches @var{regexp}.  @xref{Specified
-Headings}.
-
-@item --side-by-side
-Use the side by side output format.  @xref{Side by Side Format}.
-
-@item --speed-large-files
-Use heuristics to speed handling of large files that have numerous
-scattered small changes.  @xref{diff Performance}.
-
-@item --starting-file=@var{file}
-When comparing directories, start with the file @var{file}.  This is
-used for resuming an aborted comparison.  @xref{Comparing Directories}.
-
-@item --suppress-common-lines
-Do not print common lines in side by side format.
-@xref{Side by Side Format}.
-
-@item -t
-Expand tabs to spaces in the output, to preserve the alignment of tabs
-in the input files.  @xref{Tabs}.
-
-@item -T
-Output a tab rather than a space before the text of a line in normal or
-context format.  This causes the alignment of tabs in the line to look
-normal.  @xref{Tabs}.
-
-@item --text
-Treat all files as text and compare them line-by-line, even if they
-do not appear to be text.  @xref{Binary}.
-
-@item -u
-Use the unified output format.  @xref{Unified Format}.
-
-@item --unchanged-group-format=@var{format}
-Use @var{format} to output a group of common lines taken from both files
-in if-then-else format.  @xref{Line Group Formats}.
-
-@item --unchanged-line-format=@var{format}
-Use @var{format} to output a line common to both files in if-then-else
-format.  @xref{Line Formats}.
-
-@item --unidirectional-new-file
-When comparing directories, if a file appears only in the second
-directory of the two, treat it as present but empty in the other.
-@xref{Comparing Directories}.
-
-@item -U @var{lines}
-@itemx --unified@r{[}=@var{lines}@r{]}
-Use the unified output format, showing @var{lines} (an integer) lines of
-context, or three if @var{lines} is not given.  @xref{Unified Format}.
-For proper operation, @code{patch} typically needs at least two lines of
-context.
-
-@item -v
-@itemx --version
-Output the version number of @code{diff}.
-
-@item -w
-Ignore white space when comparing lines.  @xref{White Space}.
-
-@item -W @var{columns}
-@itemx --width=@var{columns}
-Use an output width of @var{columns} in side by side format.
-@xref{Side by Side Format}.
-
-@item -x @var{pattern}
-When comparing directories, ignore files and subdirectories whose basenames
-match @var{pattern}.  @xref{Comparing Directories}.
-
-@item -X @var{file}
-When comparing directories, ignore files and subdirectories whose basenames
-match any pattern contained in @var{file}.  @xref{Comparing Directories}.
-
-@item -y
-Use the side by side output format.  @xref{Side by Side Format}.
-@end table
-
-@node Invoking diff3, Invoking patch, Invoking diff, Top
-@chapter Invoking @code{diff3}
-@cindex invoking @code{diff3}
-@cindex @code{diff3} invocation
-
-The @code{diff3} command compares three files and outputs descriptions
-of their differences.  Its arguments are as follows:
-
-@example
-diff3 @var{options}@dots{} @var{mine} @var{older} @var{yours}
-@end example
-
-The files to compare are @var{mine}, @var{older}, and @var{yours}.
-At most one of these three file names may be @samp{-},
-which tells @code{diff3} to read the standard input for that file.
-
-An exit status of 0 means @code{diff3} was successful, 1 means some
-conflicts were found, and 2 means trouble.
-
-@menu
-* diff3 Options::		Summary of options to @code{diff3}.
-@end menu
-
-@node diff3 Options, , , Invoking diff3
-@section Options to @code{diff3}
-@cindex @code{diff3} options
-@cindex options for @code{diff3}
-
-Below is a summary of all of the options that GNU @code{diff3}
-accepts.  Multiple single letter options (unless they take an argument)
-can be combined into a single command line argument.
-
-@table @samp
-@item -a
-Treat all files as text and compare them line-by-line, even if they
-do not appear to be text.  @xref{Binary}.
-
-@item -A
-Incorporate all changes from @var{older} to @var{yours} into @var{mine},
-surrounding all conflicts with bracket lines.
-@xref{Marking Conflicts}.
-
-@item -e
-Generate an @code{ed} script that incorporates all the changes from
-@var{older} to @var{yours} into @var{mine}.  @xref{Which Changes}.
-
-@item -E
-Like @samp{-e}, except bracket lines from overlapping changes' first
-and third files.
-@xref{Marking Conflicts}.
-With @samp{-e}, an overlapping change looks like this:
-
-@example
-<<<<<<< @var{mine}
-@r{lines from @var{mine}}
-=======
-@r{lines from @var{yours}}
->>>>>>> @var{yours}
-@end example
-
-@item --ed
-Generate an @code{ed} script that incorporates all the changes from
-@var{older} to @var{yours} into @var{mine}.  @xref{Which Changes}.
-
-@item --easy-only
-Like @samp{-e}, except output only the nonoverlapping changes.
-@xref{Which Changes}.
-
-@item -i
-Generate @samp{w} and @samp{q} commands at the end of the @code{ed}
-script for System V compatibility.  This option must be combined with
-one of the @samp{-AeExX3} options, and may not be combined with @samp{-m}.
-@xref{Saving the Changed File}.
-
-@item --initial-tab
-Output a tab rather than two spaces before the text of a line in normal format.
-This causes the alignment of tabs in the line to look normal.  @xref{Tabs}.
-
-@item -L @var{label}
-@itemx --label=@var{label}
-Use the label @var{label} for the brackets output by the @samp{-A},
-@samp{-E} and @samp{-X} options.  This option may be given up to three
-times, one for each input file.  The default labels are the names of
-the input files.  Thus @samp{diff3 -L X -L Y -L Z -m A B C} acts like
-@samp{diff3 -m A B C}, except that the output looks like it came from
-files named @samp{X}, @samp{Y} and @samp{Z} rather than from files
-named @samp{A}, @samp{B} and @samp{C}.  @xref{Marking Conflicts}.
-
-@item -m
-@itemx --merge
-Apply the edit script to the first file and send the result to standard
-output.  Unlike piping the output from @code{diff3} to @code{ed}, this
-works even for binary files and incomplete lines.  @samp{-A} is assumed
-if no edit script option is specified.  @xref{Bypassing ed}.
-
-@item --overlap-only
-Like @samp{-e}, except output only the overlapping changes.
-@xref{Which Changes}.
-
-@item --show-all
-Incorporate all unmerged changes from @var{older} to @var{yours} into
-@var{mine}, surrounding all overlapping changes with bracket lines.
-@xref{Marking Conflicts}.
-
-@item --show-overlap
-Like @samp{-e}, except bracket lines from overlapping changes' first
-and third files.
-@xref{Marking Conflicts}.
-
-@item -T
-Output a tab rather than two spaces before the text of a line in normal format.
-This causes the alignment of tabs in the line to look normal.  @xref{Tabs}.
-
-@item --text
-Treat all files as text and compare them line-by-line, even if they
-do not appear to be text.  @xref{Binary}.
-
-@item -v
-@itemx --version
-Output the version number of @code{diff3}.
-
-@item -x
-Like @samp{-e}, except output only the overlapping changes.
-@xref{Which Changes}.
-
-@item -X
-Like @samp{-E}, except output only the overlapping changes.
-In other words, like @samp{-x}, except bracket changes as in @samp{-E}.
-@xref{Marking Conflicts}.
-
-@item -3
-Like @samp{-e}, except output only the nonoverlapping changes.
-@xref{Which Changes}.
-@end table
-
-@node Invoking patch, Invoking sdiff, Invoking diff3, Top
-@chapter Invoking @code{patch}
-@cindex invoking @code{patch}
-@cindex @code{patch} invocation
-
-Normally @code{patch} is invoked like this:
-
-@example
-patch <@var{patchfile}
-@end example
-
-The full format for invoking @code{patch} is:
-
-@example
-patch @var{options}@dots{} @r{[}@var{origfile} @r{[}@var{patchfile}@r{]}@r{]} @r{[}+ @var{options}@dots{} @r{[}@var{origfile}@r{]}@r{]}@dots{}
-@end example
-
-If you do not specify @var{patchfile}, or if @var{patchfile} is
-@samp{-}, @code{patch} reads the patch (that is, the @code{diff} output)
-from the standard input.
-
-You can specify one or more of the original files as @var{orig} arguments;
-each one and options for interpreting it is separated from the others with a
-@samp{+}.  @xref{Multiple Patches}, for more information.
-
-If you do not specify an input file on the command line, @code{patch}
-tries to figure out from the @dfn{leading text} (any text in the patch
-that comes before the @code{diff} output) which file to edit.  In the
-header of a context or unified diff, @code{patch} looks in lines
-beginning with @samp{***}, @samp{---}, or @samp{+++}; among those, it
-chooses the shortest name of an existing file.  Otherwise, if there is
-an @samp{Index:} line in the leading text, @code{patch} tries to use the
-file name from that line.  If @code{patch} cannot figure out the name of
-an existing file from the leading text, it prompts you for the name of
-the file to patch.
-
-If the input file does not exist or is read-only, and a suitable RCS or
-SCCS file exists, @code{patch} attempts to check out or get the file
-before proceeding.
-
-By default, @code{patch} replaces the original input file with the
-patched version, after renaming the original file into a backup file
-(@pxref{Backups}, for a description of how @code{patch} names backup
-files).  You can also specify where to put the output with the @samp{-o
-@var{output-file}} or @samp{--output=@var{output-file}} option.
-
-@menu
-* patch Directories::	Changing directory and stripping directories.
-* Backups::		Backup file names.
-* Rejects::		Reject file names.
-* patch Options::	Summary table of options to @code{patch}.
-@end menu
-
-@node patch Directories, Backups, , Invoking patch
-@section Applying Patches in Other Directories
-@cindex directories and patch
-@cindex patching directories
-
-The @samp{-d @var{directory}} or @samp{--directory=@var{directory}}
-option to @code{patch} makes directory @var{directory} the current
-directory for interpreting both file names in the patch file, and file
-names given as arguments to other options (such as @samp{-B} and
-@samp{-o}).  For example, while in a news reading program, you can patch
-a file in the @file{/usr/src/emacs} directory directly from the article
-containing the patch like this:
-
-@example
-| patch -d /usr/src/emacs
-@end example
-
-Sometimes the file names given in a patch contain leading directories,
-but you keep your files in a directory different from the one given in
-the patch.  In those cases, you can use the
-@samp{-p@r{[}@var{number}@r{]}} or @samp{--strip@r{[}=@var{number}@r{]}}
-option to set the file name strip count to @var{number}.  The strip
-count tells @code{patch} how many slashes, along with the directory
-names between them, to strip from the front of file names.  @samp{-p}
-with no @var{number} given is equivalent to @samp{-p0}.  By default,
-@code{patch} strips off all leading directories, leaving just the base file
-names, except that when a file name given in the patch is a relative
-file name and all of its leading directories already exist, @code{patch} does
-not strip off the leading directory.  (A @dfn{relative} file name is one
-that does not start with a slash.)
-
-@code{patch} looks for each file (after any slashes have been stripped)
-in the current directory, or if you used the @samp{-d @var{directory}}
-option, in that directory.
-
-For example, suppose the file name in the patch file is
-@file{/gnu/src/emacs/etc/NEWS}.  Using @samp{-p} or @samp{-p0} gives the
-entire file name unmodified, @samp{-p1} gives
-@file{gnu/src/emacs/etc/NEWS} (no leading slash), @samp{-p4} gives
-@file{etc/NEWS}, and not specifying @samp{-p} at all gives @file{NEWS}.
-
-@node Backups, Rejects, patch Directories, Invoking patch
-@section Backup File Names
-@cindex backup file names
-
-Normally, @code{patch} renames an original input file into a backup file
-by appending to its name the extension @samp{.orig}, or @samp{~} on
-systems that do not support long file names.  The @samp{-b
-@var{backup-suffix}} or @samp{--suffix=@var{backup-suffix}} option uses
-@var{backup-suffix} as the backup extension instead.
-
-Alternately, you can specify the extension for backup files with the
-@code{SIMPLE_BACKUP_SUFFIX} environment variable, which the options
-override.
-
-@code{patch} can also create numbered backup files the way GNU Emacs
-does.  With this method, instead of having a single backup of each file,
-@code{patch} makes a new backup file name each time it patches a file.
-For example, the backups of a file named @file{sink} would be called,
-successively, @file{sink.~1~}, @file{sink.~2~}, @file{sink.~3~}, etc.
-
-The @samp{-V @var{backup-style}} or
-@samp{--version-control=@var{backup-style}} option takes as an argument
-a method for creating backup file names.  You can alternately control
-the type of backups that @code{patch} makes with the
-@code{VERSION_CONTROL} environment variable, which the @samp{-V} option
-overrides.  The value of the @code{VERSION_CONTROL} environment variable
-and the argument to the @samp{-V} option are like the GNU Emacs
-@code{version-control} variable (@pxref{Backups,
-emacs, The GNU Emacs Manual}, for more information on backup versions in
-Emacs).  They also recognize synonyms that are more descriptive.  The
-valid values are listed below; unique abbreviations are acceptable.
-
-@table @samp
-@item t
-@itemx numbered
-Always make numbered backups.
-
-@item nil
-@itemx existing
-Make numbered backups of files that already have them, simple backups of
-the others.  This is the default.
-
-@item never
-@itemx simple
-Always make simple backups.
-@end table
-
-Alternately, you can tell @code{patch} to prepend a prefix, such as a
-directory name, to produce backup file names.  The @samp{-B
-@var{backup-prefix}} or @samp{--prefix=@var{backup-prefix}} option makes
-backup files by prepending @var{backup-prefix} to them.  If you use this
-option, @code{patch} ignores any @samp{-b} option that you give.
-
-If the backup file already exists, @code{patch} creates a new backup
-file name by changing the first lowercase letter in the last component
-of the file name into uppercase.  If there are no more lowercase letters
-in the name, it removes the first character from the name.  It repeats
-this process until it comes up with a backup file name that does not
-already exist.
-
-If you specify the output file with the @samp{-o} option, that file is
-the one that is backed up, not the input file.
-
-@node Rejects, patch Options, Backups, Invoking patch
-@section Reject File Names
-@cindex reject file names
-
-The names for reject files (files containing patches that @code{patch}
-could not find a place to apply) are normally the name of the output
-file with @samp{.rej} appended (or @samp{#} on systems that do not
-support long file names).
-
-Alternatively, you can tell @code{patch} to place all of the rejected
-patches in a single file.  The @samp{-r @var{reject-file}} or
-@samp{--reject-file=@var{reject-file}} option uses @var{reject-file} as
-the reject file name.
-
-@node patch Options, , Rejects, Invoking patch
-@section Options to @code{patch}
-@cindex @code{patch} options
-@cindex options for @code{patch}
-
-Here is a summary of all of the options that @code{patch} accepts.
-Older versions of @code{patch} do not accept long-named options or the
-@samp{-t}, @samp{-E}, or @samp{-V} options.
-
-Multiple single-letter options that do not take an argument can be
-combined into a single command line argument (with only one dash).
-Brackets ([ and ]) indicate that an option takes an optional argument.
-
-@table @samp
-@item -b @var{backup-suffix}
-Use @var{backup-suffix} as the backup extension instead of
-@samp{.orig} or @samp{~}.  @xref{Backups}.
-
-@item -B @var{backup-prefix}
-Use @var{backup-prefix} as a prefix to the backup file name.  If this
-option is specified, any @samp{-b} option is ignored.  @xref{Backups}.
-
-@item --batch
-Do not ask any questions.  @xref{patch Messages}.
-
-@item -c
-@itemx --context
-Interpret the patch file as a context diff.  @xref{patch Input}.
-
-@item -d @var{directory}
-@itemx --directory=@var{directory}
-Makes directory @var{directory} the current directory for interpreting
-both file names in the patch file, and file names given as arguments to
-other options.  @xref{patch Directories}.
-
-@item -D @var{name}
-Make merged if-then-else output using @var{format}.  @xref{If-then-else}.
-
-@item --debug=@var{number}
-Set internal debugging flags.  Of interest only to @code{patch}
-patchers.
-
-@item -e
-@itemx --ed
-Interpret the patch file as an @code{ed} script.  @xref{patch Input}.
-
-@item -E
-Remove output files that are empty after the patches have been applied.
-@xref{Empty Files}.
-
-@item -f
-Assume that the user knows exactly what he or she is doing, and do not
-ask any questions.  @xref{patch Messages}.
-
-@item -F @var{lines}
-Set the maximum fuzz factor to @var{lines}.  @xref{Inexact}.
-
-@item --force
-Assume that the user knows exactly what he or she is doing, and do not
-ask any questions.  @xref{patch Messages}.
-
-@item --forward
-Ignore patches that @code{patch} thinks are reversed or already applied.
-See also @samp{-R}.  @xref{Reversed Patches}.
-
-@item --fuzz=@var{lines}
-Set the maximum fuzz factor to @var{lines}.  @xref{Inexact}.
-
-@item --help
-Print a summary of the options that @code{patch} recognizes, then exit.
-
-@item --ifdef=@var{name}
-Make merged if-then-else output using @var{format}.  @xref{If-then-else}.
-
-@item --ignore-white-space
-@itemx -l
-Let any sequence of white space in the patch file match any sequence of
-white space in the input file.  @xref{Changed White Space}.
-
-@item -n
-@itemx --normal
-Interpret the patch file as a normal diff.  @xref{patch Input}.
-
-@item -N
-Ignore patches that @code{patch} thinks are reversed or already applied.
-See also @samp{-R}.  @xref{Reversed Patches}.
-
-@item -o @var{output-file}
-@itemx --output=@var{output-file}
-Use @var{output-file} as the output file name.  @xref{patch Options}.
-
-@item -p@r{[}@var{number}@r{]}
-Set the file name strip count to @var{number}.  @xref{patch Directories}.
-
-@item --prefix=@var{backup-prefix}
-Use @var{backup-prefix} as a prefix to the backup file name.  If this
-option is specified, any @samp{-b} option is ignored.  @xref{Backups}.
-
-@item --quiet
-Work silently unless an error occurs.  @xref{patch Messages}.
-
-@item -r @var{reject-file}
-Use @var{reject-file} as the reject file name.  @xref{Rejects}.
-
-@item -R
-Assume that this patch was created with the old and new files swapped.
-@xref{Reversed Patches}.
-
-@item --reject-file=@var{reject-file}
-Use @var{reject-file} as the reject file name.  @xref{Rejects}.
-
-@item --remove-empty-files
-Remove output files that are empty after the patches have been applied.
-@xref{Empty Files}.
-
-@item --reverse
-Assume that this patch was created with the old and new files swapped.
-@xref{Reversed Patches}.
-
-@item -s
-Work silently unless an error occurs.  @xref{patch Messages}.
-
-@item -S
-Ignore this patch from the patch file, but continue looking for the next
-patch in the file.  @xref{Multiple Patches}.
-
-@item --silent
-Work silently unless an error occurs.  @xref{patch Messages}.
-
-@item --skip
-Ignore this patch from the patch file, but continue looking for the next
-patch in the file.  @xref{Multiple Patches}.
-
-@item --strip@r{[}=@var{number}@r{]}
-Set the file name strip count to @var{number}.  @xref{patch Directories}.
-
-@item --suffix=@var{backup-suffix}
-Use @var{backup-suffix} as the backup extension instead of
-@samp{.orig} or @samp{~}.  @xref{Backups}.
-
-@item -t
-Do not ask any questions.  @xref{patch Messages}.
-
-@item -u
-@itemx --unified
-Interpret the patch file as a unified diff.  @xref{patch Input}.
-
-@item -v
-Output the revision header and patch level of @code{patch}.
-
-@item -V @var{backup-style}
-Select the kind of backups to make.  @xref{Backups}.
-
-@item --version
-Output the revision header and patch level of @code{patch}, then exit.
-
-@item --version=control=@var{backup-style}
-Select the kind of backups to make.  @xref{Backups}.
-
-@item -x @var{number}
-Set internal debugging flags.  Of interest only to @code{patch}
-patchers.
-@end table
-
-@node Invoking sdiff, Incomplete Lines, Invoking patch, Top
-@chapter Invoking @code{sdiff}
-@cindex invoking @code{sdiff}
-@cindex @code{sdiff} invocation
-
-The @code{sdiff} command merges two files and interactively outputs the
-results.  Its arguments are as follows:
-
-@example
-sdiff -o @var{outfile} @var{options}@dots{} @var{from-file} @var{to-file}
-@end example
-
-This merges @var{from-file} with @var{to-file}, with output to @var{outfile}.
-If @var{from-file} is a directory and @var{to-file} is not, @code{sdiff}
-compares the file in @var{from-file} whose file name is that of @var{to-file},
-and vice versa.  @var{from-file} and @var{to-file} may not both be
-directories.
-
-@code{sdiff} options begin with @samp{-}, so normally @var{from-file}
-and @var{to-file} may not begin with @samp{-}.  However, @samp{--} as an
-argument by itself treats the remaining arguments as file names even if
-they begin with @samp{-}.  You may not use @samp{-} as an input file.
-
-An exit status of 0 means no differences were found, 1 means some
-differences were found, and 2 means trouble.
-
-@code{sdiff} without @samp{-o} (or @samp{--output}) produces a
-side-by-side difference.  This usage is obsolete; use @samp{diff
---side-by-side} instead.
-
-@menu
-* sdiff Options::	Summary of options to @code{diff}.
-@end menu
-
-@node sdiff Options, , , Invoking sdiff
-@section Options to @code{sdiff}
-@cindex @code{sdiff} options
-@cindex options for @code{sdiff}
-
-Below is a summary of all of the options that GNU @code{sdiff} accepts.
-Each option has two equivalent names, one of which is a single
-letter preceded by @samp{-}, and the other of which is a long name
-preceded by @samp{--}.  Multiple single letter options (unless they take
-an argument) can be combined into a single command line argument.  Long
-named options can be abbreviated to any unique prefix of their name.
-
-@table @samp
-@item -a
-Treat all files as text and compare them line-by-line, even if they
-do not appear to be text.  @xref{Binary}.
-
-@item -b
-Ignore changes in amount of white space.  @xref{White Space}.
-
-@item -B
-Ignore changes that just insert or delete blank lines.  @xref{Blank
-Lines}.
-
-@item -d
-Change the algorithm to perhaps find a smaller set of changes.  This
-makes @code{sdiff} slower (sometimes much slower).  @xref{diff
-Performance}.
-
-@item -H
-Use heuristics to speed handling of large files that have numerous
-scattered small changes.  @xref{diff Performance}.
-
-@item --expand-tabs
-Expand tabs to spaces in the output, to preserve the alignment of tabs
-in the input files.  @xref{Tabs}.
-
-@item -i
-Ignore changes in case; consider upper- and lower-case to be the same.
-@xref{Case Folding}.
-
-@item -I @var{regexp}
-Ignore changes that just insert or delete lines that match @var{regexp}.
-@xref{Specified Folding}.
-
-@item --ignore-all-space
-Ignore white space when comparing lines.  @xref{White Space}.
-
-@item --ignore-blank-lines
-Ignore changes that just insert or delete blank lines.  @xref{Blank
-Lines}.
-
-@item --ignore-case
-Ignore changes in case; consider upper- and lower-case to be the same.
-@xref{Case Folding}.
-
-@item --ignore-matching-lines=@var{regexp}
-Ignore changes that just insert or delete lines that match @var{regexp}.
-@xref{Specified Folding}.
-
-@item --ignore-space-change
-Ignore changes in amount of white space.
-@xref{White Space}.
-
-@item -l
-@itemx --left-column
-Print only the left column of two common lines.
-@xref{Side by Side Format}.
-
-@item --minimal
-Change the algorithm to perhaps find a smaller set of changes.  This
-makes @code{sdiff} slower (sometimes much slower).  @xref{diff
-Performance}.
-
-@item -o @var{file}
-@itemx --output=@var{file}
-Put merged output into @var{file}.  This option is required for merging.
-
-@item -s
-@itemx --suppress-common-lines
-Do not print common lines.  @xref{Side by Side Format}.
-
-@item --speed-large-files
-Use heuristics to speed handling of large files that have numerous
-scattered small changes.  @xref{diff Performance}.
-
-@item -t
-Expand tabs to spaces in the output, to preserve the alignment of tabs
-in the input files.  @xref{Tabs}.
-
-@item --text
-Treat all files as text and compare them line-by-line, even if they
-do not appear to be text.  @xref{Binary}.
-
-@item -v
-@itemx --version
-Output the version number of @code{sdiff}.
-
-@item -w @var{columns}
-@itemx --width=@var{columns}
-Use an output width of @var{columns}.  @xref{Side by Side Format}.
-Note that for historical reasons, this option is @samp{-W} in @code{diff},
-@samp{-w} in @code{sdiff}.
-
-@item -W
-Ignore horizontal white space when comparing lines.  @xref{White Space}.
-Note that for historical reasons, this option is @samp{-w} in @code{diff},
-@samp{-W} in @code{sdiff}.
-@end table
-
-@node Incomplete Lines, Projects, Invoking sdiff, Top
-@chapter Incomplete Lines
-@cindex incomplete lines
-@cindex full lines
-@cindex newline treatment by @code{diff}
-
-When an input file ends in a non-newline character, its last line is
-called an @dfn{incomplete line} because its last character is not a
-newline.  All other lines are called @dfn{full lines} and end in a
-newline character.  Incomplete lines do not match full lines unless
-differences in white space are ignored (@pxref{White Space}).
-
-An incomplete line is normally distinguished on output from a full line
-by a following line that starts with @samp{\}.  However, the RCS format
-(@pxref{RCS}) outputs the incomplete line as-is, without any trailing
-newline or following line.  The side by side format normally represents
-incomplete lines as-is, but in some cases uses a @samp{\} or @samp{/}
-gutter marker; @xref{Side by Side}.  The if-then-else line format
-preserves a line's incompleteness with @samp{%L}, and discards the
-newline with @samp{%l}; @xref{Line Formats}.  Finally, with the
-@code{ed} and forward @code{ed} output formats (@pxref{Output Formats})
-@code{diff} cannot represent an incomplete line, so it pretends there
-was a newline and reports an error.
-
-For example, suppose @file{F} and @file{G} are one-byte files that
-contain just @samp{f} and @samp{g}, respectively.  Then @samp{diff F G}
-outputs
-
-@example
-1c1
-< f
-\ No newline at end of file
----
-> g
-\ No newline at end of file
-@end example
-
-@noindent
-(The exact message may differ in non-English locales.)
-@samp{diff -n F G} outputs the following without a trailing newline:
-
-@example
-d1 1
-a1 1
-g
-@end example
-
-@samp{diff -e F G} reports two errors and outputs the following:
-
-@example
-1c
-g
-.
-@end example
-
-@node Projects, Concept Index, Incomplete Lines, Top
-@chapter Future Projects
-
-Here are some ideas for improving GNU @code{diff} and @code{patch}.  The
-GNU project has identified some improvements as potential programming
-projects for volunteers.  You can also help by reporting any bugs that
-you find.
-
-If you are a programmer and would like to contribute something to the
-GNU project, please consider volunteering for one of these projects.  If
-you are seriously contemplating work, please write to
-@samp{gnu@@prep.ai.mit.edu} to coordinate with other volunteers.
-
-@menu
-* Shortcomings::	Suggested projects for improvements.
-* Bugs::		Reporting bugs.
-@end menu
-
-@node Shortcomings, Bugs, , Projects
-@section Suggested Projects for Improving GNU @code{diff} and @code{patch}
-@cindex projects for directories
-
-One should be able to use GNU @code{diff} to generate a patch from any
-pair of directory trees, and given the patch and a copy of one such
-tree, use @code{patch} to generate a faithful copy of the other.
-Unfortunately, some changes to directory trees cannot be expressed using
-current patch formats; also, @code{patch} does not handle some of the
-existing formats.  These shortcomings motivate the following suggested
-projects.
-
-@menu
-* Changing Structure::	Handling changes to the directory structure.
-* Special Files::	Handling symbolic links, device special files, etc.
-* Unusual File Names::	Handling file names that contain unusual characters.
-* Arbitrary Limits::	Patching non-text files.
-* Large Files::		Handling files that do not fit in memory.
-* Ignoring Changes::	Ignoring certain changes while showing others.
-@end menu
-
-@node Changing Structure, Special Files, , Shortcomings
-@subsection Handling Changes to the Directory Structure
-@cindex directory structure changes
-
-@code{diff} and @code{patch} do not handle some changes to directory
-structure.  For example, suppose one directory tree contains a directory
-named @samp{D} with some subsidiary files, and another contains a file
-with the same name @samp{D}.  @samp{diff -r} does not output enough
-information for @code{patch} to transform the the directory subtree into
-the file.
-
-There should be a way to specify that a file has been deleted without
-having to include its entire contents in the patch file.  There should
-also be a way to tell @code{patch} that a file was renamed, even if
-there is no way for @code{diff} to generate such information.
-
-These problems can be fixed by extending the @code{diff} output format
-to represent changes in directory structure, and extending @code{patch}
-to understand these extensions.
-
-@node Special Files, Unusual File Names, Changing Structure, Shortcomings
-@subsection Files that are Neither Directories Nor Regular Files
-@cindex special files
-
-Some files are neither directories nor regular files: they are unusual
-files like symbolic links, device special files, named pipes, and
-sockets.  Currently, @code{diff} treats symbolic links like regular files;
-it treats other special files like regular files if they are specified
-at the top level, but simply reports their presence when comparing
-directories.  This means that @code{patch} cannot represent changes
-to such files.  For example, if you change which file a symbolic link
-points to, @code{diff} outputs the difference between the two files,
-instead of the change to the symbolic link.
-
-@c This might not be a good idea; is it wise for root to install devices
-@c this way?
-@code{diff} should optionally report changes to special files specially,
-and @code{patch} should be extended to understand these extensions.
-
-@node Unusual File Names, Arbitrary Limits, Special Files, Shortcomings
-@subsection File Names that Contain Unusual Characters
-@cindex file names with unusual characters
-
-When a file name contains an unusual character like a newline or
-white space, @samp{diff -r} generates a patch that @code{patch} cannot
-parse.  The problem is with format of @code{diff} output, not just with
-@code{patch}, because with odd enough file names one can cause
-@code{diff} to generate a patch that is syntactically correct but
-patches the wrong files.  The format of @code{diff} output should be
-extended to handle all possible file names.
-
-@node Arbitrary Limits, Large Files, Unusual File Names, Shortcomings
-@subsection Arbitrary Limits
-@cindex binary file patching
-
-GNU @code{diff} can analyze files with arbitrarily long lines and files
-that end in incomplete lines.  However, @code{patch} cannot patch such
-files.  The @code{patch} internal limits on line lengths should be
-removed, and @code{patch} should be extended to parse @code{diff}
-reports of incomplete lines.
-
-@node Large Files, Ignoring Changes, Arbitrary Limits, Shortcomings
-@subsection Handling Files that Do Not Fit in Memory
-@cindex large files
-
-@code{diff} operates by reading both files into memory.  This method
-fails if the files are too large, and @code{diff} should have a fallback.
-
-One way to do this is to scan the files sequentially to compute hash
-codes of the lines and put the lines in equivalence classes based only
-on hash code.  Then compare the files normally.  This does produce some
-false matches.
-
-Then scan the two files sequentially again, checking each match to see
-whether it is real.  When a match is not real, mark both the
-``matching'' lines as changed.  Then build an edit script as usual.
-
-The output routines would have to be changed to scan the files
-sequentially looking for the text to print.
-
-@node Ignoring Changes,, Large Files, Shortcomings
-@subsection Ignoring Certain Changes
-
-It would be nice to have a feature for specifying two strings, one in
-@var{from-file} and one in @var{to-file}, which should be considered to
-match.  Thus, if the two strings are @samp{foo} and @samp{bar}, then if
-two lines differ only in that @samp{foo} in file 1 corresponds to
-@samp{bar} in file 2, the lines are treated as identical.
-
-It is not clear how general this feature can or should be, or
-what syntax should be used for it.
-
-@node Bugs, , Shortcomings, Projects
-@section Reporting Bugs
-@cindex bug reports
-@cindex reporting bugs
-
-If you think you have found a bug in GNU @code{cmp}, @code{diff},
-@code{diff3}, @code{sdiff}, or @code{patch}, please report it by
-electronic mail to @samp{bug-gnu-utils@@prep.ai.mit.edu}.  Send as
-precise a description of the problem as you can, including sample input
-files that produce the bug, if applicable.
-
-Because Larry Wall has not released a new version of @code{patch} since
-mid 1988 and the GNU version of @code{patch} has been changed since
-then, please send bug reports for @code{patch} by electronic mail to
-both @samp{bug-gnu-utils@@prep.ai.mit.edu} and
-@samp{lwall@@netlabs.com}.
-
-@node Concept Index, , Projects, Top
-@unnumbered Concept Index
-
-@printindex cp
-
-@shortcontents
-@contents
-@bye