archive: specfile support (--pretty=format: in archive files)

Add support for a new attribute, specfile.  Files marked as being
specfiles are expanded by git-archive when they are written to an
archive.  It has no effect on worktree files.  The same placeholders
as those for the option --pretty=format: of git-log et al. can be
used.

The attribute is useful for creating auto-updating specfiles.  It is
limited by the underlying function format_commit_message(), though.
E.g. currently there is no placeholder for git-describe like output,
and expanded specfiles can't contain NUL bytes.  That can be fixed
in format_commit_message() later and will then benefit users of
git-log, too.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/archive-tar.c b/archive-tar.c
index 66fe3e375b..c0d95dab0d 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -17,6 +17,7 @@ static unsigned long offset;
 static time_t archive_time;
 static int tar_umask = 002;
 static int verbose;
+static const struct commit *commit;
 
 /* writes out the whole block, but only if it is full */
 static void write_if_needed(void)
@@ -285,7 +286,8 @@ static int write_tar_entry(const unsigned char *sha1,
 		buffer = NULL;
 		size = 0;
 	} else {
-		buffer = convert_sha1_file(path.buf, sha1, mode, &type, &size);
+		buffer = sha1_file_to_archive(path.buf, sha1, mode, &type,
+		                              &size, commit);
 		if (!buffer)
 			die("cannot read %s", sha1_to_hex(sha1));
 	}
@@ -304,6 +306,7 @@ int write_tar_archive(struct archiver_args *args)
 
 	archive_time = args->time;
 	verbose = args->verbose;
+	commit = args->commit;
 
 	if (args->commit_sha1)
 		write_global_extended_header(args->commit_sha1);