Support +<src>:<dst> format in push as well.

Signed-off-by: NJunio C Hamano <junkio@cox.net>

cache.h

@@ -309,6 +309,7 @@ struct ref {
 	struct ref *next;
 	unsigned char old_sha1[20];
 	unsigned char new_sha1[20];
+	unsigned char force;
 	struct ref *peer_ref; /* when renaming */
 	char name[0];
 };

connect.c

@@ -82,15 +82,26 @@ int path_match(const char *path, int nr, char **match)
 struct refspec {
 	char *src;
 	char *dst;
+	char force;
 };
 
+/*
+ * A:B means fast forward remote B with local A.
+ * +A:B means overwrite remote B with local A.
+ * +A is a shorthand for +A:A.
+ * A is a shorthand for A:A.
+ */
 static struct refspec *parse_ref_spec(int nr_refspec, char **refspec)
 {
 	int i;
-	struct refspec *rs = xmalloc(sizeof(*rs) * (nr_refspec + 1));
+	struct refspec *rs = xcalloc(sizeof(*rs), (nr_refspec + 1));
 	for (i = 0; i < nr_refspec; i++) {
 		char *sp, *dp, *ep;
 		sp = refspec[i];
+		if (*sp == '+') {
+			rs[i].force = 1;
+			sp++;
+		}
 		ep = strchr(sp, ':');
 		if (ep) {
 			dp = ep + 1;
@@ -216,8 +227,10 @@ static int match_explicit_refs(struct ref *src, struct ref *dst,
 			error("dst ref %s receives from more than one src.",
 			      matched_dst->name);
 		}
-		else
+		else {
 			matched_dst->peer_ref = matched_src;
+			matched_dst->force = rs[i].force;
+		}
 	}
 	return -errs;
 }

send-pack.c

@@ -206,7 +206,8 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 		/* This part determines what can overwrite what.
 		 * The rules are:
 		 *
-		 * (0) you can always use --force.
+		 * (0) you can always use --force or +A:B notation to
+		 *     selectively force individual ref pairs.
 		 *
 		 * (1) if the old thing does not exist, it is OK.
 		 *
@@ -218,16 +219,19 @@ static int send_pack(int in, int out, int nr_refspec, char **refspec)
 		 *     descendant of old, it is OK.
 		 */
 
-		if (!force_update && !is_zero_sha1(ref->old_sha1)) {
+		if (!force_update &&
+		    !is_zero_sha1(ref->old_sha1) &&
+		    !ref->force) {
 			if (!has_sha1_file(ref->old_sha1)) {
 				error("remote '%s' object %s does not "
 				      "exist on local",
 				      ref->name, sha1_to_hex(ref->old_sha1));
 				continue;
 			}
+
 			/* We assume that local is fsck-clean.  Otherwise
-			 * you _could_ have a old tag which points at
-			 * something you do not have which may or may not
+			 * you _could_ have an old tag which points at
+			 * something you do not have, which may or may not
 			 * be a commit.
 			 */
 			if (!ref_newer(ref->peer_ref->new_sha1,