Add a -n option to pkg_create(1), to inhibit duplicate work.

When run without this option, multiple runs of `pkg_create -Rb' will
recreate common packages multiple times.  This can take a lot of time
for large packages.  With the -n option `pkg_create -b' checks with
stat(2) and skips packages that already exist.

Note that this may *not* be safe of the existing output file is not
really a package, or if it has been corrupted, modified or otherwise
tinkered with between subsequent pkg_create runs.  For this and POLA
reasons, the default behavior is to *rebuild* the packages, and the -n
option can be used when we know it is `safe' to run in no-regenerate
mode.

Inspired by:	A post to freebsd-questions
	 	by Matthias Apitz < matthias.apitz at oclc.org >
Reviewed by:	marcus, flz
Approved by:	marcus
MFC after:	2 weeks

4 files changed, 42 insertions, 5 deletions

diff --git a/usr.sbin/pkg_install/create/create.h b/usr.sbin/pkg_install/create/create.h
index 9450170..310aba0 100644
--- a/usr.sbin/pkg_install/create/create.h
+++ b/usr.sbin/pkg_install/create/create.h
@@ -46,6 +46,7 @@ extern char	PlayPen[];
 extern int	Dereference;
 extern int	PlistOnly;
 extern int	Recursive;
+extern int	Regenerate;
 
 enum zipper {NONE, GZIP, BZIP, BZIP2 };
 extern enum zipper	Zipper;
diff --git a/usr.sbin/pkg_install/create/main.c b/usr.sbin/pkg_install/create/main.c
index c35cfd6..ea15b91 100644
--- a/usr.sbin/pkg_install/create/main.c
+++ b/usr.sbin/pkg_install/create/main.c
@@ -16,7 +16,7 @@ __FBSDID("$FreeBSD$");
 #include "lib.h"
 #include "create.h"
 
-static char Options[] = "EGYNORhjvxyzf:p:P:C:c:d:i:I:k:K:r:t:X:D:m:s:S:o:b:";
+static char Options[] = "EGYNnORhjvxyzf:p:P:C:c:d:i:I:k:K:r:t:X:D:m:s:S:o:b:";
 
 match_t	MatchType	= MATCH_GLOB;
 char	*Prefix		= NULL;
@@ -41,6 +41,7 @@ char	PlayPen[FILENAME_MAX];
 int	Dereference	= FALSE;
 int	PlistOnly	= FALSE;
 int	Recursive	= FALSE;
+int	Regenerate	= TRUE;
 #if defined(__FreeBSD_version) && __FreeBSD_version >= 500039
 enum zipper	Zipper  = BZIP2;
 #else
@@ -192,6 +193,10 @@ main(int argc, char **argv)
 	    Recursive = TRUE;
 	    break;
 
+	case 'n':
+		Regenerate = FALSE;
+		break;
+
 	case '?':
 	default:
 	    usage();
@@ -228,7 +233,7 @@ static void
 usage()
 {
     fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n",
-"usage: pkg_create [-YNOhjvyz] [-C conflicts] [-P pkgs] [-p prefix]",
+"usage: pkg_create [-YNOhjnvyz] [-C conflicts] [-P pkgs] [-p prefix]",
 "                  [-i iscript] [-I piscript] [-k dscript] [-K pdscript]",
 "                  [-r rscript] [-s srcdir] [-S basedir]",
 "                  [-t template] [-X excludefile]",
diff --git a/usr.sbin/pkg_install/create/perform.c b/usr.sbin/pkg_install/create/perform.c
index 77ec1f2..505826e 100644
--- a/usr.sbin/pkg_install/create/perform.c
+++ b/usr.sbin/pkg_install/create/perform.c
@@ -28,6 +28,8 @@ __FBSDID("$FreeBSD$");
 #include <libgen.h>
 #include <signal.h>
 #include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 #include <sys/syslimits.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -336,6 +338,7 @@ pkg_perform(char **pkgs)
 static void
 make_dist(const char *homedir, const char *pkg, const char *suff, Package *plist)
 {
+    struct stat sb;
     char tball[FILENAME_MAX];
     PackingList p;
     int ret;
@@ -355,6 +358,16 @@ make_dist(const char *homedir, const char *pkg, const char *suff, Package *plist
     else
 	snprintf(tball, FILENAME_MAX, "%s/%s.%s", homedir, pkg, suff);
 
+    /*
+     * If the package tarball exists already, and we are running in `no
+     * clobber' mode, skip this package.
+     */
+    if (stat(tball, &sb) == 0 && Regenerate == FALSE) {
+	if (Verbose)
+	    printf("Skipping package '%s'.  It already exists.\n", tball);
+	return;
+    }
+
     args[nargs++] = "-c";
     args[nargs++] = "-f";
     args[nargs++] = tball;
diff --git a/usr.sbin/pkg_install/create/pkg_create.1 b/usr.sbin/pkg_install/create/pkg_create.1
index 6fb6d58..a65cfaf 100644
--- a/usr.sbin/pkg_install/create/pkg_create.1
+++ b/usr.sbin/pkg_install/create/pkg_create.1
@@ -23,7 +23,7 @@
 .\" [jkh] Took John's changes back and made some additional extensions for
 .\" better integration with FreeBSD's new ports collection.
 .\"
-.Dd November 8, 2005
+.Dd May 27, 2008
 .Dt PKG_CREATE 1
 .Os
 .Sh NAME
@@ -31,7 +31,7 @@
 .Nd a utility for creating software package distributions
 .Sh SYNOPSIS
 .Nm
-.Op Fl YNOhjvyz
+.Op Fl YNOhjnvyz
 .Op Fl C Ar conflicts
 .Op Fl P Ar pkgs
 .Op Fl p Ar prefix
@@ -52,7 +52,7 @@
 .Fl f Ar packlist
 .Ar pkg-filename
 .Nm
-.Op Fl EGYNRhvxy
+.Op Fl EGYNRhnvxy
 .Fl b Ar pkg-name
 .Op Ar pkg-filename
 .Sh DESCRIPTION
@@ -350,6 +350,24 @@ Use extended (modern) regular expressions for
 .It Fl G
 Use exact matching for
 .Ar pkg-name .
+.It Fl n
+Run in
+.Dq no clobber
+mode.
+If a package tarball exists, the
+.Nm
+utility will not overwrite it.
+This is useful, for example, when multiple packages are saved with
+several consecutive runs of
+.Nm
+with the
+.Fl Rb
+options.
+Saving common dependencies multiple times would do a lot of duplicate
+work in this case.
+The
+.Fl n
+option avoids repackaging common dependencies multiple times.
 .El
 .Sh PACKING LIST DETAILS
 The