builtin-remote: add set-head subcommand

Provide a porcelain command for setting and deleting
$GIT_DIR/remotes/<remote>/HEAD.

While we're at it, document what $GIT_DIR/remotes/<remote>/HEAD is all
about.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/builtin-remote.c b/builtin-remote.c
index 4543cf0..640e4da 100644
--- a/builtin-remote.c
+++ b/builtin-remote.c
@@ -12,6 +12,7 @@ static const char * const builtin_remote_usage[] = {
 	"git remote add [-t <branch>] [-m <master>] [-f] [--mirror] <name> <url>",
 	"git remote rename <old> <new>",
 	"git remote rm <name>",
+	"git remote set-head <name> [-a | -d | <branch>]",
 	"git remote show [-n] <name>",
 	"git remote prune [-n | --dry-run] <name>",
 	"git remote [-v | --verbose] update [group]",
@@ -792,6 +793,65 @@ static int show(int argc, const char **argv)
 	return result;
 }
 
+static int set_head(int argc, const char **argv)
+{
+	int i, opt_a = 0, opt_d = 0, result = 0;
+	struct strbuf buf = STRBUF_INIT, buf2 = STRBUF_INIT;
+	char *head_name = NULL;
+
+	struct option options[] = {
+		OPT_GROUP("set-head specific options"),
+		OPT_BOOLEAN('a', "auto", &opt_a,
+			    "set refs/remotes/<name>/HEAD according to remote"),
+		OPT_BOOLEAN('d', "delete", &opt_d,
+			    "delete refs/remotes/<name>/HEAD"),
+		OPT_END()
+	};
+	argc = parse_options(argc, argv, options, builtin_remote_usage, 0);
+	if (argc)
+		strbuf_addf(&buf, "refs/remotes/%s/HEAD", argv[0]);
+
+	if (!opt_a && !opt_d && argc == 2) {
+		head_name = xstrdup(argv[1]);
+	} else if (opt_a && !opt_d && argc == 1) {
+		struct ref_states states;
+		memset(&states, 0, sizeof(states));
+		get_remote_ref_states(argv[0], &states, GET_HEAD_NAMES);
+		if (!states.heads.nr)
+			result |= error("Cannot determine remote HEAD");
+		else if (states.heads.nr > 1) {
+			result |= error("Multiple remote HEAD branches. "
+					"Please choose one explicitly with:");
+			for (i = 0; i < states.heads.nr; i++)
+				fprintf(stderr, "  git remote set-head %s %s\n",
+					argv[0], states.heads.items[i].string);
+		} else
+			head_name = xstrdup(states.heads.items[0].string);
+		free_remote_ref_states(&states);
+	} else if (opt_d && !opt_a && argc == 1) {
+		if (delete_ref(buf.buf, NULL, REF_NODEREF))
+			result |= error("Could not delete %s", buf.buf);
+	} else
+		usage_with_options(builtin_remote_usage, options);
+
+	if (head_name) {
+		unsigned char sha1[20];
+		strbuf_addf(&buf2, "refs/remotes/%s/%s", argv[0], head_name);
+		/* make sure it's valid */
+		if (!resolve_ref(buf2.buf, sha1, 1, NULL))
+			result |= error("Not a valid ref: %s", buf2.buf);
+		else if (create_symref(buf.buf, buf2.buf, "remote set-head"))
+			result |= error("Could not setup %s", buf.buf);
+		if (opt_a)
+			printf("%s/HEAD set to %s\n", argv[0], head_name);
+		free(head_name);
+	}
+
+	strbuf_release(&buf);
+	strbuf_release(&buf2);
+	return result;
+}
+
 static int prune(int argc, const char **argv)
 {
 	int dry_run = 0, result = 0;
@@ -962,6 +1022,8 @@ int cmd_remote(int argc, const char **argv, const char *prefix)
 		result = mv(argc, argv);
 	else if (!strcmp(argv[0], "rm"))
 		result = rm(argc, argv);
+	else if (!strcmp(argv[0], "set-head"))
+		result = set_head(argc, argv);
 	else if (!strcmp(argv[0], "show"))
 		result = show(argc, argv);
 	else if (!strcmp(argv[0], "prune"))