Teach send-pack a mirror mode

Existing "git push --all" is almost perfect for backing up to
another repository, except that "--all" only means "all
branches" in modern git, and it does not delete old branches and
tags that exist at the back-up repository that you have removed
from your local repository.

This teaches "git-send-pack" a new "--mirror" option.  The
difference from the "--all" option are that (1) it sends all
refs, not just branches, and (2) it deletes old refs you no
longer have on the local side from the remote side.

Original patch by Junio C Hamano.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 34 insertions, 12 deletions

diff --git a/builtin-send-pack.c b/builtin-send-pack.c
index 5a0f5c6..d42164e 100644
--- a/builtin-send-pack.c
+++ b/builtin-send-pack.c
@@ -8,7 +8,7 @@
 #include "send-pack.h"
 
 static const char send_pack_usage[] =
-"git-send-pack [--all] [--dry-run] [--force] [--receive-pack=<git-receive-pack>] [--verbose] [--thin] [<host>:]<directory> [<ref>...]\n"
+"git-send-pack [--all | --mirror] [--dry-run] [--force] [--receive-pack=<git-receive-pack>] [--verbose] [--thin] [<host>:]<directory> [<ref>...]\n"
 "  --all and explicit <ref> specification are mutually exclusive.";
 
 static struct send_pack_args args = {
@@ -227,6 +227,12 @@ static int do_send_pack(int in, int out, struct remote *remote, const char *dest
 	int allow_deleting_refs = 0;
 	int expect_status_report = 0;
 	int shown_dest = 0;
+	int flags = MATCH_REFS_NONE;
+
+	if (args.send_all)
+		flags |= MATCH_REFS_ALL;
+	if (args.send_mirror)
+		flags |= MATCH_REFS_MIRROR;
 
 	/* No funny business with the matcher */
 	remote_tail = get_remote_heads(in, &remote_refs, 0, NULL, REF_NORMAL);
@@ -242,7 +248,7 @@ static int do_send_pack(int in, int out, struct remote *remote, const char *dest
 	if (!remote_tail)
 		remote_tail = &remote_refs;
 	if (match_refs(local_refs, remote_refs, &remote_tail,
-		       nr_refspec, refspec, args.send_all))
+					       nr_refspec, refspec, flags))
 		return -1;
 
 	if (!remote_refs) {
@@ -259,20 +265,28 @@ static int do_send_pack(int in, int out, struct remote *remote, const char *dest
 		char old_hex[60], *new_hex;
 		int will_delete_ref;
 		const char *pretty_ref;
-		const char *pretty_peer;
+		const char *pretty_peer = NULL; /* only used when not deleting */
+		const unsigned char *new_sha1;
 
-		if (!ref->peer_ref)
-			continue;
+		if (!ref->peer_ref) {
+			if (!args.send_mirror)
+				continue;
+			new_sha1 = null_sha1;
+		}
+		else
+			new_sha1 = ref->peer_ref->new_sha1;
 
 		if (!shown_dest) {
 			fprintf(stderr, "To %s\n", dest);
 			shown_dest = 1;
 		}
 
+		will_delete_ref = is_null_sha1(new_sha1);
+
 		pretty_ref = prettify_ref(ref->name);
-		pretty_peer = prettify_ref(ref->peer_ref->name);
+		if (!will_delete_ref)
+			pretty_peer = prettify_ref(ref->peer_ref->name);
 
-		will_delete_ref = is_null_sha1(ref->peer_ref->new_sha1);
 		if (will_delete_ref && !allow_deleting_refs) {
 			fprintf(stderr, " ! %-*s %s (remote does not support deleting refs)\n",
 					SUMMARY_WIDTH, "[rejected]", pretty_ref);
@@ -280,7 +294,7 @@ static int do_send_pack(int in, int out, struct remote *remote, const char *dest
 			continue;
 		}
 		if (!will_delete_ref &&
-		    !hashcmp(ref->old_sha1, ref->peer_ref->new_sha1)) {
+		    !hashcmp(ref->old_sha1, new_sha1)) {
 			if (args.verbose)
 				fprintf(stderr, " = %-*s %s -> %s\n",
 					SUMMARY_WIDTH, "[up to date]",
@@ -312,8 +326,7 @@ static int do_send_pack(int in, int out, struct remote *remote, const char *dest
 		    !is_null_sha1(ref->old_sha1) &&
 		    !ref->force) {
 			if (!has_sha1_file(ref->old_sha1) ||
-			    !ref_newer(ref->peer_ref->new_sha1,
-				       ref->old_sha1)) {
+			    !ref_newer(new_sha1, ref->old_sha1)) {
 				/* We do not have the remote ref, or
 				 * we know that the remote ref is not
 				 * an ancestor of what we are trying to
@@ -328,7 +341,7 @@ static int do_send_pack(int in, int out, struct remote *remote, const char *dest
 				continue;
 			}
 		}
-		hashcpy(ref->new_sha1, ref->peer_ref->new_sha1);
+		hashcpy(ref->new_sha1, new_sha1);
 		if (!will_delete_ref)
 			new_refs++;
 		strcpy(old_hex, sha1_to_hex(ref->old_sha1));
@@ -459,6 +472,10 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 				args.dry_run = 1;
 				continue;
 			}
+			if (!strcmp(arg, "--mirror")) {
+				args.send_mirror = 1;
+				continue;
+			}
 			if (!strcmp(arg, "--force")) {
 				args.force_update = 1;
 				continue;
@@ -483,7 +500,12 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 	}
 	if (!dest)
 		usage(send_pack_usage);
-	if (heads && args.send_all)
+	/*
+	 * --all and --mirror are incompatible; neither makes sense
+	 * with any refspecs.
+	 */
+	if ((heads && (args.send_all || args.send_mirror)) ||
+					(args.send_all && args.send_mirror))
 		usage(send_pack_usage);
 
 	if (remote_name) {