I think your git command is not in the path inherited by the Alfred process
Can you type in a Terminal and post the results
type -P git
type -ap git
Then in Alfred create a new blank workflow, say hotkey to script, oh hold on ... here, try this:
See what the output is (it's posted as a large type notification and copied to the clipboard for you to paste in here)
$ echo $PATH
$ which git
$ type -P git
$ type -ap git
The from the workflow:
PATH = /usr/bin:/bin:/usr/sbin:/sbin
which git = [/usr/bin/git]
So the Cheaters workflow works for me as I have two gits installed.
1. I add a load of paths to the Info.plist and export them. e.g.
resulting from getGitPath.alfredworkflow in:
PATH = /usr/local/bin:/usr/local/sbin:/usr/local/share/npm/bin:/usr/bin:/bin:/usr/sbin:/sbin
which git = [/usr/local/bin/git]
2. I spend a little time finding the right git in my workflow.
I'll opt for 2 and submit an update, but I'd like to see your output if possible to make sure I am thinking along the right lines.