POSIX.1e-style Extended Attribute support

This commit implements storing/reading POSIX.1e-style extended
attribute information in "pax" format archives.  An outline of the
storage format is in the tar.5 manpage.  The archive_read_extract()
function has code to restore those archives to disk for Linux; FreeBSD
implementation is forthcoming.

Many thanks to Jaakko Heinonen for finding flaws in earlier
proposals and doing the bulk of the coding in this work.

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/libarchive/tar.5 b/lib/libarchive/tar.5
index d46e1b5..242a3d0 100644
--- a/lib/libarchive/tar.5
+++ b/lib/libarchive/tar.5
@@ -399,6 +399,21 @@ Schilling's
 .Cm SCHILY.*
 extensions can store all of the data from
 .Va struct stat .
+.It Cm LIBARCHIVE.xattr. Ns Ar namespace Ns . Ns Ar key
+Libarchive stores POSIX.1e-style extended attributes using
+keys of this form.  The
+.Ar key
+value is URL-encoded:
+All non-ASCII characters and the two special characters
+.Dq =
+and
+.Dq %
+are encoded as
+.Dq %
+followed by two uppercase hexadecimal digits.
+The value of this key is the extended attribute value
+encoded in base 64.
+XXX Detail the base-64 format here XXX
 .It Cm VENDOR.*
 XXX document other vendor-specific extensions XXX
 .El