receive-pack hooks updates.

The earlier one conflated update and post-update hooks for no
good reason.  Correct that ugly hack.  Now post-update hooks
will take the list of successfully updated refs.

Signed-off-by: Junio C Hamano <junkio@cox.net>

run-command.h

@@ -11,6 +11,7 @@ enum {
 	ERR_RUN_COMMAND_WAITPID_NOEXIT,
 };
 
+int run_command_v(int argc, char **argv);
 int run_command(const char *cmd, ...);
 
 #endif