[PATCH] Teach ls-tree about commit objects

Updates ls-tree.c to use read_tree_with_tree_or_commit_sha1()
function.  The command can take either tree or commit IDs with
this patch.

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