Make "git rev-list" be a builtin

This was surprisingly easy. The diff is truly minimal: rename "main()" to
"cmd_rev_list()" in rev-list.c, and rename the whole file to reflect its
new built-in status.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git.c

@@ -50,6 +50,7 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
 		{ "count-objects", cmd_count_objects },
 		{ "diff", cmd_diff },
 		{ "grep", cmd_grep },
+		{ "rev-list", cmd_rev_list },
 	};
 	int i;