push: teach --recurse-submodules the on-demand option

When using this option git will search for all submodules that
have changed in the revisions to be send. It will then try to
push the currently checked out branch of each submodule.

This helps when a user has finished working on a change which
involves submodules and just wants to push everything in one go.

Signed-off-by: Fredrik Gustafsson <iveqy@iveqy.com>
Mentored-by: Jens Lehmann <Jens.Lehmann@web.de>
Mentored-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

submodule.c

@@ -410,6 +410,54 @@ int find_unpushed_submodules(unsigned char new_sha1[20],
 	return needs_pushing->nr;
 }
 
+static int push_submodule(const char *path)
+{
+	if (add_submodule_odb(path))
+		return 1;
+
+	if (for_each_remote_ref_submodule(path, has_remote, NULL) > 0) {
+		struct child_process cp;
+		const char *argv[] = {"push", NULL};
+
+		memset(&cp, 0, sizeof(cp));
+		cp.argv = argv;
+		cp.env = local_repo_env;
+		cp.git_cmd = 1;
+		cp.no_stdin = 1;
+		cp.dir = path;
+		if (run_command(&cp))
+			return 0;
+		close(cp.out);
+	}
+
+	return 1;
+}
+
+int push_unpushed_submodules(unsigned char new_sha1[20], const char *remotes_name)
+{
+	int i, ret = 1;
+	struct string_list needs_pushing;
+
+	memset(&needs_pushing, 0, sizeof(struct string_list));
+	needs_pushing.strdup_strings = 1;
+
+	if (!find_unpushed_submodules(new_sha1, remotes_name, &needs_pushing))
+		return 1;
+
+	for (i = 0; i < needs_pushing.nr; i++) {
+		const char *path = needs_pushing.items[i].string;
+		fprintf(stderr, "Pushing submodule '%s'\n", path);
+		if (!push_submodule(path)) {
+			fprintf(stderr, "Unable to push submodule '%s'\n", path);
+			ret = 0;
+		}
+	}
+
+	string_list_clear(&needs_pushing, 0);
+
+	return ret;
+}
+
 static int is_submodule_commit_present(const char *path, unsigned char sha1[20])
 {
 	int is_present = 0;