It appears that git push commands are hard to support in Windows because the use of ssh requires a ssh-agent daemon to be running, and it's not an obvious windows service. Some of the powershell wrappers etc. use work-arounds using tools like Cygwin.
In the end, I decided it wasn't worth the extra effort, and will use non-MATLAB tools for the git push and interactive commands (git pull works fine from within MATLAB, though!).
