bundle: Use OFS_DELTA in bundle files

git-bundle first appeared in 2e0afaf ("Add git-bundle") in Feb 2007,
and first shipped in Git 1.5.1.

However, OFS_DELTA is an even earlier invention, coming about in
eb32d23 ("introduce delta objects with offset to base") in Sep 2006,
and first shipped in Git 1.4.4.5.

OFS_DELTA is smaller, about 3.2%-5% smaller, and is typically faster
to access than REF_DELTA because the exact location of the delta base
is available after parsing the object header.  Since all bundle aware
versions of Git are also OFS_DELTA aware, just make it the default.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

bundle.c

@@ -200,7 +200,7 @@ int create_bundle(struct bundle_header *header, const char *path,
 	int bundle_fd = -1;
 	int bundle_to_stdout;
 	const char **argv_boundary = xmalloc((argc + 4) * sizeof(const char *));
-	const char **argv_pack = xmalloc(5 * sizeof(const char *));
+	const char **argv_pack = xmalloc(6 * sizeof(const char *));
 	int i, ref_count = 0;
 	char buffer[1024];
 	struct rev_info revs;
@@ -346,7 +346,8 @@ int create_bundle(struct bundle_header *header, const char *path,
 	argv_pack[1] = "--all-progress-implied";
 	argv_pack[2] = "--stdout";
 	argv_pack[3] = "--thin";
-	argv_pack[4] = NULL;
+	argv_pack[4] = "--delta-base-offset";
+	argv_pack[5] = NULL;
 	memset(&rls, 0, sizeof(rls));
 	rls.argv = argv_pack;
 	rls.in = -1;