Teach 'git remote' how to cleanup stale tracking branches.

Since it can be annoying to manually cleanup 40 tracking branches
which were removed by the remote system, 'git remote prune <n>'
can now be used to delete any tracking branches under <n> which
are no longer available on the remote system.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-remote.txt

@@ -12,6 +12,7 @@ SYNOPSIS
 'git-remote'
 'git-remote' add <name> <url>
 'git-remote' show <name>
+'git-remote' prune <name>
 
 DESCRIPTION
 -----------
@@ -26,6 +27,10 @@ update remote-tracking branches <name>/<branch>.
 
 In the third form, gives some information about the remote <name>.
 
+In the fourth form, deletes all stale tracking branches under <name>.
+These stale branches have already been removed from the remote repository
+referenced by <name>, but are still locally available in "remotes/<name>".
+
 The remote configuration is achieved using the `remote.origin.url` and
 `remote.origin.fetch` configuration variables.  (See
 gitlink:git-config[1]).

git-remote.perl

@@ -200,7 +200,7 @@ sub show_mapping {
 		print "    @$new\n";
 	}
 	if (@$stale) {
-		print "  Stale tracking branches in remotes/$name (you'd better remove them)\n";
+		print "  Stale tracking branches in remotes/$name (use 'git remote prune')\n";
 		print "    @$stale\n";
 	}
 	if (@$tracked) {
@@ -209,6 +209,23 @@ sub show_mapping {
 	}
 }
 
+sub prune_remote {
+	my ($name, $ls_remote) = @_;
+	if (!exists $remote->{$name}) {
+		print STDERR "No such remote $name\n";
+		return;
+	}
+	my $info = $remote->{$name};
+	update_ls_remote($ls_remote, $info);
+
+	my ($new, $stale, $tracked) = list_mapping($name, $info);
+	my $prefix = "refs/remotes/$name";
+	foreach my $to_prune (@$stale) {
+		my @v = $git->command(qw(rev-parse --verify), "$prefix/$to_prune");
+		$git->command(qw(update-ref -d), "$prefix/$to_prune", $v[0]);
+	}
+}
+
 sub show_remote {
 	my ($name, $ls_remote) = @_;
 	if (!exists $remote->{$name}) {
@@ -270,6 +287,25 @@ sub add_remote {
 		show_remote($ARGV[$i], $ls_remote);
 	}
 }
+elsif ($ARGV[0] eq 'prune') {
+	my $ls_remote = 1;
+	my $i;
+	for ($i = 1; $i < @ARGV; $i++) {
+		if ($ARGV[$i] eq '-n') {
+			$ls_remote = 0;
+		}
+		else {
+			last;
+		}
+	}
+	if ($i >= @ARGV) {
+		print STDERR "Usage: git remote prune <remote>\n";
+		exit(1);
+	}
+	for (; $i < @ARGV; $i++) {
+		prune_remote($ARGV[$i], $ls_remote);
+	}
+}
 elsif ($ARGV[0] eq 'add') {
 	if (@ARGV != 3) {
 		print STDERR "Usage: git remote add <name> <url>\n";
@@ -281,5 +317,6 @@ sub add_remote {
 	print STDERR "Usage: git remote\n";
 	print STDERR "       git remote add <name> <url>\n";
 	print STDERR "       git remote show <name>\n";
+	print STDERR "       git remote prune <name>\n";
 	exit(1);
 }