This sort of thing has been discussed before:
Basically, some systems I'm working on have a version of git too old to support the --short format, so I added in the old status comparison removed in this commit. The systems I'm working on are running git 18.104.22.168 and 22.214.171.124, so I gated the old-style status checking to <1.6.4. I couldn't find documentation anywhere of when the --short format was first supported, so that version comparison can and should be changed if someone knows better. Also, I'm not a shell scripting maven, so it's possible my code is horribly unconventional or wrong, and I'd appreciate feedback on that. Thanks.
Workaround for git status on old git
Apparently the issue still exists in 126.96.36.199
Merge branch 'master' of git://github.com/robbyrussell/oh-my-zsh into…
#1654 was chosen as the workaround for this issue, I believe.