add special "matching refs" refspec

This patch provides a way to specify "push matching heads" using a
special refspec ":".  This is useful because it allows "push = +:"
as a way to specify that matching refs will be pushed but, in addition,
forced updates will be allowed, which was not possible before.

Signed-off-by: Paolo Bonzini <bonzini@gnu.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -46,12 +46,6 @@ specified, the same ref that <src> referred to locally).  If
 the optional leading plus `+` is used, the remote ref is updated
 even if it does not result in a fast forward update.
 +
-Note: If no explicit refspec is found, (that is neither
-on the command line nor in any Push line of the
-corresponding remotes file---see below), then "matching" heads are
-pushed: for every head that exists on the local side, the remote side is
-updated if a head of the same name already exists on the remote side.
-+
 `tag <tag>` means the same as `refs/tags/<tag>:refs/tags/<tag>`.
 +
 A parameter <ref> without a colon pushes the <ref> from the source
@@ -59,6 +53,13 @@ repository to the destination repository under the same name.
 +
 Pushing an empty <src> allows you to delete the <dst> ref from
 the remote repository.
++
+The special refspec `:` (or `+:` to allow non-fast forward updates)
+directs git to push "matching" heads: for every head that exists on
+the local side, the remote side is updated if a head of the same name
+already exists on the remote side.  This is the default operation mode
+if no explicit refspec is found (that is neither on the command line
+nor in any Push line of the corresponding remotes file---see below).
 
 \--all::
 	Instead of naming each ref to push, specifies that all

builtin-send-pack.c

@@ -537,9 +537,17 @@ static void verify_remote_names(int nr_heads, const char **heads)
 	int i;
 
 	for (i = 0; i < nr_heads; i++) {
+		const char *local = heads[i];
 		const char *remote = strrchr(heads[i], ':');
 
-		remote = remote ? (remote + 1) : heads[i];
+		if (*local == '+')
+			local++;
+
+		/* A matching refspec is okay.  */
+		if (remote == local && remote[1] == '\0')
+			continue;
+
+		remote = remote ? (remote + 1) : local;
 		switch (check_ref_format(remote)) {
 		case 0: /* ok */
 		case CHECK_REF_FORMAT_ONELEVEL:

remote.c

@@ -429,6 +429,16 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
 		}
 
 		rhs = strrchr(lhs, ':');
+
+		/*
+		 * Before going on, special case ":" (or "+:") as a refspec
+		 * for matching refs.
+		 */
+		if (!fetch && rhs == lhs && rhs[1] == '\0') {
+			rs[i].matching = 1;
+			continue;
+		}
+
 		if (rhs) {
 			rhs++;
 			rlen = strlen(rhs);
@@ -842,7 +852,7 @@ static int match_explicit(struct ref *src, struct ref *dst,
 	const char *dst_value = rs->dst;
 	char *dst_guess;
 
-	if (rs->pattern)
+	if (rs->pattern || rs->matching)
 		return errs;
 
 	matched_src = matched_dst = NULL;
@@ -932,13 +942,23 @@ static const struct refspec *check_pattern_match(const struct refspec *rs,
 						 const struct ref *src)
 {
 	int i;
+	int matching_refs = -1;
 	for (i = 0; i < rs_nr; i++) {
+		if (rs[i].matching &&
+		    (matching_refs == -1 || rs[i].force)) {
+			matching_refs = i;
+			continue;
+		}
+
 		if (rs[i].pattern &&
 		    !prefixcmp(src->name, rs[i].src) &&
 		    src->name[strlen(rs[i].src)] == '/')
 			return rs + i;
 	}
-	return NULL;
+	if (matching_refs != -1)
+		return rs + matching_refs;
+	else
+		return NULL;
 }
 
 /*
@@ -949,11 +969,16 @@ static const struct refspec *check_pattern_match(const struct refspec *rs,
 int match_refs(struct ref *src, struct ref *dst, struct ref ***dst_tail,
 	       int nr_refspec, const char **refspec, int flags)
 {
-	struct refspec *rs =
-		parse_push_refspec(nr_refspec, (const char **) refspec);
+	struct refspec *rs;
 	int send_all = flags & MATCH_REFS_ALL;
 	int send_mirror = flags & MATCH_REFS_MIRROR;
+	static const char *default_refspec[] = { ":", 0 };
 
+	if (!nr_refspec) {
+		nr_refspec = 1;
+		refspec = default_refspec;
+	}
+	rs = parse_push_refspec(nr_refspec, (const char **) refspec);
 	if (match_explicit_refs(src, dst, dst_tail, rs, nr_refspec))
 		return -1;
 
@@ -964,48 +989,50 @@ int match_refs(struct ref *src, struct ref *dst, struct ref ***dst_tail,
 		char *dst_name;
 		if (src->peer_ref)
 			continue;
-		if (nr_refspec) {
-			pat = check_pattern_match(rs, nr_refspec, src);
-			if (!pat)
-				continue;
-		}
-		else if (!send_mirror && prefixcmp(src->name, "refs/heads/"))
+
+		pat = check_pattern_match(rs, nr_refspec, src);
+		if (!pat)
+			continue;
+
+		if (pat->matching) {
 			/*
 			 * "matching refs"; traditionally we pushed everything
 			 * including refs outside refs/heads/ hierarchy, but
 			 * that does not make much sense these days.
 			 */
-			continue;
+			if (!send_mirror && prefixcmp(src->name, "refs/heads/"))
+				continue;
+			dst_name = xstrdup(src->name);
 
-		if (pat) {
+		} else {
 			const char *dst_side = pat->dst ? pat->dst : pat->src;
 			dst_name = xmalloc(strlen(dst_side) +
 					   strlen(src->name) -
 					   strlen(pat->src) + 2);
 			strcpy(dst_name, dst_side);
 			strcat(dst_name, src->name + strlen(pat->src));
-		} else
-			dst_name = xstrdup(src->name);
+		}
 		dst_peer = find_ref_by_name(dst, dst_name);
-		if (dst_peer && dst_peer->peer_ref)
-			/* We're already sending something to this ref. */
-			goto free_name;
+		if (dst_peer) {
+			if (dst_peer->peer_ref)
+				/* We're already sending something to this ref. */
+				goto free_name;
+
+		} else {
+			if (pat->matching && !(send_all || send_mirror))
+				/*
+				 * Remote doesn't have it, and we have no
+				 * explicit pattern, and we don't have
+				 * --all nor --mirror.
+				 */
+				goto free_name;
 
-		if (!dst_peer && !nr_refspec && !(send_all || send_mirror))
-			/*
-			 * Remote doesn't have it, and we have no
-			 * explicit pattern, and we don't have
-			 * --all nor --mirror.
-			 */
-			goto free_name;
-		if (!dst_peer) {
 			/* Create a new one and link it */
 			dst_peer = make_linked_ref(dst_name, dst_tail);
 			hashcpy(dst_peer->new_sha1, src->new_sha1);
 		}
 		dst_peer->peer_ref = src;
-		if (pat)
-			dst_peer->force = pat->force;
+		dst_peer->force = pat->force;
 	free_name:
 		free(dst_name);
 	}

remote.h

@@ -46,6 +46,7 @@ int remote_has_url(struct remote *remote, const char *url);
 struct refspec {
 	unsigned force : 1;
 	unsigned pattern : 1;
+	unsigned matching : 1;
 
 	char *src;
 	char *dst;

t/t5511-refspec.sh

@@ -23,10 +23,13 @@ test_refspec () {
 }
 
 test_refspec push ''						invalid
-test_refspec push ':'						invalid
+test_refspec push ':'
+test_refspec push '::'						invalid
+test_refspec push '+:'
 
 test_refspec fetch ''
 test_refspec fetch ':'
+test_refspec fetch '::'						invalid
 
 test_refspec push 'refs/heads/*:refs/remotes/frotz/*'
 test_refspec push 'refs/heads/*:refs/remotes/frotz'		invalid

t/t5516-fetch-push.sh

@@ -165,6 +165,47 @@ test_expect_success 'push with matching heads' '
 
 '
 
+test_expect_success 'push with matching heads on the command line' '
+
+	mk_test heads/master &&
+	git push testrepo : &&
+	check_push_result $the_commit heads/master
+
+'
+
+test_expect_success 'failed (non-fast-forward) push with matching heads' '
+
+	mk_test heads/master &&
+	git push testrepo : &&
+	git commit --amend -massaged &&
+	! git push testrepo &&
+	check_push_result $the_commit heads/master &&
+	git reset --hard $the_commit
+
+'
+
+test_expect_success 'push --force with matching heads' '
+
+	mk_test heads/master &&
+	git push testrepo : &&
+	git commit --amend -massaged &&
+	git push --force testrepo &&
+	! check_push_result $the_commit heads/master &&
+	git reset --hard $the_commit
+
+'
+
+test_expect_success 'push with matching heads and forced update' '
+
+	mk_test heads/master &&
+	git push testrepo : &&
+	git commit --amend -massaged &&
+	git push testrepo +: &&
+	! check_push_result $the_commit heads/master &&
+	git reset --hard $the_commit
+
+'
+
 test_expect_success 'push with no ambiguity (1)' '
 
 	mk_test heads/master &&