Make git-resolve-script only write MERGE_HEAD if a merge actually
occurred. All merge failures leave ORIG_HEAD and LAST_MERGE
behind (instead of ORIG_HEAD and MERGE_HEAD).
Use git-rev-parse to expand arguments (and check for bad ones).
Signed-off-by: Dan Holmsand <holmsand@gmail.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>