As stated in comment above:
git pull
is (usually) shorthand for doing a fetch
then merge
.
Check that git fetch
works first.
Further later research shows that this may be a bug in a specific version of msysgit, https://code.google.com/p/msysgit/issues/detail?id=249 So try upgrading that also (always prudent advice).
Additionally, a few googles for "git: 'pull' is not a git command
" turned up quite a few choices on various fixes, based on which platform you are working on, but most turned out to be a missing path to git-core, so also check those out.