push: use remote.$name.push as a refmap

Since f269048 (fetch: opportunistically update tracking refs,
2013-05-11), we stopped taking a non-storing refspec given on the
command line of "git fetch" literally, and instead started mapping
it via remote.$name.fetch refspecs.  This allows

    $ git fetch origin master

from the 'origin' repository, which is configured with

    [remote "origin"]
        fetch = +refs/heads/*:refs/remotes/origin/*

to update refs/remotes/origin/master with the result, as if the
command line were

    $ git fetch origin +master:refs/remotes/origin/master

to reduce surprises and improve usability.  Before that change, a
refspec on the command line without a colon was only to fetch the
history and leave the result in FETCH_HEAD, without updating the
remote-tracking branches.

When you are simulating a fetch from you by your mothership with a
push by you into your mothership, instead of having:

    [remote "satellite"]
        fetch = +refs/heads/*:refs/remotes/satellite/*

on the mothership repository and running:

    mothership$ git fetch satellite

you would have:

    [remote "mothership"]
        push = +refs/heads/*:refs/remotes/satellite/*

on your satellite machine, and run:

    satellite$ git push mothership

Because we so far did not make the corresponding change to the push
side, this command:

    satellite$ git push mothership master

does _not_ allow you on the satellite to only push 'master' out but
still to the usual destination (i.e. refs/remotes/satellite/master).

Implement the logic to map an unqualified refspec given on the
command line via the remote.$name.push refspec.  This will bring a
bit more symmetry between "fetch" and "push".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -56,8 +56,13 @@ it can be any arbitrary "SHA-1 expression", such as `master~4` or
 +
 The <dst> tells which ref on the remote side is updated with this
 push. Arbitrary expressions cannot be used here, an actual ref must
-be named. If `:`<dst> is omitted, the same ref as <src> will be
-updated.
+be named.
+If `git push [<repository>]` without any `<refspec>` argument is set to
+update some ref at the destination with `<src>` with
+`remote.<repository>.push` configuration variable, `:<dst>` part can
+be omitted---such a push will update a ref that `<src>` normally updates
+without any `<refspec>` on the command line.  Otherwise, missing
+`:<dst>` means to update the same ref as the `<src>`.
 +
 The object referenced by <src> is used to update the <dst> reference
 on the remote side.  By default this is only allowed if <dst> is not

builtin/push.c

@@ -35,9 +35,38 @@ static void add_refspec(const char *ref)
 	refspec[refspec_nr-1] = ref;
 }
 
-static void set_refspecs(const char **refs, int nr)
+static const char *map_refspec(const char *ref,
+			       struct remote *remote, struct ref *local_refs)
 {
+	struct ref *matched = NULL;
+
+	/* Does "ref" uniquely name our ref? */
+	if (count_refspec_match(ref, local_refs, &matched) != 1)
+		return ref;
+
+	if (remote->push) {
+		struct refspec query;
+		memset(&query, 0, sizeof(struct refspec));
+		query.src = matched->name;
+		if (!query_refspecs(remote->push, remote->push_refspec_nr, &query) &&
+		    query.dst) {
+			struct strbuf buf = STRBUF_INIT;
+			strbuf_addf(&buf, "%s%s:%s",
+				    query.force ? "+" : "",
+				    query.src, query.dst);
+			return strbuf_detach(&buf, NULL);
+		}
+	}
+
+	return ref;
+}
+
+static void set_refspecs(const char **refs, int nr, const char *repo)
+{
+	struct remote *remote = NULL;
+	struct ref *local_refs = NULL;
 	int i;
+
 	for (i = 0; i < nr; i++) {
 		const char *ref = refs[i];
 		if (!strcmp("tag", ref)) {
@@ -56,6 +85,13 @@ static void set_refspecs(const char **refs, int nr)
 				die(_("--delete only accepts plain target ref names"));
 			strbuf_addf(&delref, ":%s", ref);
 			ref = strbuf_detach(&delref, NULL);
+		} else if (!strchr(ref, ':')) {
+			if (!remote) {
+				/* lazily grab remote and local_refs */
+				remote = remote_get(repo);
+				local_refs = get_local_heads();
+			}
+			ref = map_refspec(ref, remote, local_refs);
 		}
 		add_refspec(ref);
 	}
@@ -487,7 +523,7 @@ int cmd_push(int argc, const char **argv, const char *prefix)
 
 	if (argc > 0) {
 		repo = argv[0];
-		set_refspecs(argv + 1, argc - 1);
+		set_refspecs(argv + 1, argc - 1, repo);
 	}
 
 	rc = do_push(repo, flags);

remote.c

@@ -821,7 +821,7 @@ static int match_name_with_pattern(const char *key, const char *name,
 	return ret;
 }
 
-static int query_refspecs(struct refspec *refs, int ref_count, struct refspec *query)
+int query_refspecs(struct refspec *refs, int ref_count, struct refspec *query)
 {
 	int i;
 	int find_src = !query->src;
@@ -955,9 +955,9 @@ void sort_ref_list(struct ref **l, int (*cmp)(const void *, const void *))
 	*l = llist_mergesort(*l, ref_list_get_next, ref_list_set_next, cmp);
 }
 
-static int count_refspec_match(const char *pattern,
-			       struct ref *refs,
-			       struct ref **matched_ref)
+int count_refspec_match(const char *pattern,
+			struct ref *refs,
+			struct ref **matched_ref)
 {
 	int patlen = strlen(pattern);
 	struct ref *matched_weak = NULL;

remote.h

@@ -128,6 +128,7 @@ struct ref *alloc_ref(const char *name);
 struct ref *copy_ref(const struct ref *ref);
 struct ref *copy_ref_list(const struct ref *ref);
 void sort_ref_list(struct ref **, int (*cmp)(const void *, const void *));
+extern int count_refspec_match(const char *, struct ref *refs, struct ref **matched_ref);
 int ref_compare_name(const void *, const void *);
 
 int check_ref_type(const struct ref *ref, int flags);
@@ -158,6 +159,7 @@ struct refspec *parse_fetch_refspec(int nr_refspec, const char **refspec);
 
 void free_refspec(int nr_refspec, struct refspec *refspec);
 
+extern int query_refspecs(struct refspec *specs, int nr, struct refspec *query);
 char *apply_refspecs(struct refspec *refspecs, int nr_refspec,
 		     const char *name);
 

t/t5516-fetch-push.sh

@@ -1126,6 +1126,51 @@ test_expect_success 'fetch follows tags by default' '
 	test_cmp expect actual
 '
 
+test_expect_success 'pushing a specific ref applies remote.$name.push as refmap' '
+	mk_test testrepo heads/master &&
+	rm -fr src dst &&
+	git init src &&
+	git init --bare dst &&
+	(
+		cd src &&
+		git pull ../testrepo master &&
+		git branch next &&
+		git config remote.dst.url ../dst &&
+		git config remote.dst.push "+refs/heads/*:refs/remotes/src/*" &&
+		git push dst master &&
+		git show-ref refs/heads/master |
+		sed -e "s|refs/heads/|refs/remotes/src/|" >../dst/expect
+	) &&
+	(
+		cd dst &&
+		test_must_fail git show-ref refs/heads/next &&
+		test_must_fail git show-ref refs/heads/master &&
+		git show-ref refs/remotes/src/master >actual
+	) &&
+	test_cmp dst/expect dst/actual
+'
+
+test_expect_success 'with no remote.$name.push, it is not used as refmap' '
+	mk_test testrepo heads/master &&
+	rm -fr src dst &&
+	git init src &&
+	git init --bare dst &&
+	(
+		cd src &&
+		git pull ../testrepo master &&
+		git branch next &&
+		git config remote.dst.url ../dst &&
+		git push dst master &&
+		git show-ref refs/heads/master >../dst/expect
+	) &&
+	(
+		cd dst &&
+		test_must_fail git show-ref refs/heads/next &&
+		git show-ref refs/heads/master >actual
+	) &&
+	test_cmp dst/expect dst/actual
+'
+
 test_expect_success 'push does not follow tags by default' '
 	mk_test testrepo heads/master &&
 	rm -fr src dst &&