Make git-rerere a builtin

The perl version used modules which are non-standard in some setups.
This patch brings the full power of rerere to a wider audience.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git.c

@@ -245,6 +245,7 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
 		{ "push", cmd_push, RUN_SETUP },
 		{ "read-tree", cmd_read_tree, RUN_SETUP },
 		{ "repo-config", cmd_repo_config },
+		{ "rerere", cmd_rerere, RUN_SETUP },
 		{ "rev-list", cmd_rev_list, RUN_SETUP },
 		{ "rev-parse", cmd_rev_parse, RUN_SETUP },
 		{ "rm", cmd_rm, RUN_SETUP },