[PATCH 8/6] let the GIT native protocol use offsets to delta base when possible

[Nicolas Pitre <nico@cam.org>]

There is no reason not to always do this when both ends agree.  
Therefore a client that can accept offsets to delta base always sends 
the "ofs-delta" flag.  The server will stream a pack with or without 
offset to delta base depending on whether that flag is provided or not 
with no additional cost.

Signed-off-by: Nicolas Pitre <nico@cam.org>

---

Yeah... 8th of 6 should mean this is pretty much over now.

Since this depends on support that has been merged into the pu branch I 
diffed this against pu.

diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
diff --git a/fetch-pack.c b/fetch-pack.c
index 99ac08b..90b7940 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -166,12 +166,13 @@ static int find_common(int fd[2], unsign
 		}
 
 		if (!fetching)
-			packet_write(fd[1], "want %s%s%s%s%s\n",
+			packet_write(fd[1], "want %s%s%s%s%s%s\n",
 				     sha1_to_hex(remote),
 				     (multi_ack ? " multi_ack" : ""),
 				     (use_sideband == 2 ? " side-band-64k" : ""),
 				     (use_sideband == 1 ? " side-band" : ""),
-				     (use_thin_pack ? " thin-pack" : ""));
+				     (use_thin_pack ? " thin-pack" : ""),
+				     " ofs-delta");
 		else
 			packet_write(fd[1], "want %s\n", sha1_to_hex(remote));
 		fetching++;
diff --git a/upload-pack.c b/upload-pack.c
index 4e53edd..4572fff 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -22,7 +22,7 @@ #define REACHABLE	(1u << 15)
 static unsigned long oldest_have;
 
 static int multi_ack, nr_our_refs;
-static int use_thin_pack;
+static int use_thin_pack, use_ofs_delta;
 static struct object_array have_obj;
 static struct object_array want_obj;
 static unsigned int timeout;
@@ -143,7 +143,9 @@ static void create_pack_file(void)
 		close(pu_pipe[1]);
 		close(pe_pipe[0]);
 		close(pe_pipe[1]);
-		execl_git_cmd("pack-objects", "--stdout", "--progress", NULL);
+		execl_git_cmd("pack-objects", "--stdout", "--progress",
+			      use_ofs_delta ? "--delta-base-offset" : NULL,
+			      NULL);
 		kill(pid_rev_list, SIGKILL);
 		die("git-upload-pack: unable to exec git-pack-objects");
 	}
@@ -476,6 +478,8 @@ static void receive_needs(void)
 			multi_ack = 1;
 		if (strstr(line+45, "thin-pack"))
 			use_thin_pack = 1;
+		if (strstr(line+45, "ofs-delta"))
+			use_ofs_delta = 1;
 		if (strstr(line+45, "side-band-64k"))
 			use_sideband = LARGE_PACKET_MAX;
 		else if (strstr(line+45, "side-band"))
@@ -501,7 +505,7 @@ static void receive_needs(void)
 
 static int send_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
 {
-	static const char *capabilities = "multi_ack thin-pack side-band side-band-64k";
+	static const char *capabilities = "multi_ack thin-pack side-band side-band-64k ofs-delta";
 	struct object *o = parse_object(sha1);
 
 	if (!o)