Prompt always shows files changed in git 1.8.1.2 on MacOS

Git 1.7.9.5 in Ubuntu 12.04 says "nothing to commit (working directory clean)". But git 1.8.1.2 on MacOS says "nothing to commit, working directory clean", which doesn't work here. It always says that files are changed when they're not. Haven't tried it on Ubuntu 13.04 yet.

This fix will work on both versions of git.