initial work to make gitrepo work on windows

[jtnord]

see #745

Currently this does not fully work as the local environment is still being picked up for GIT_SSH etc..

27 :   inflating: gitRepo/.git/refs/heads/master
28 :    creating: gitRepo/.git/refs/tags/
29 :   inflating: gitRepo/foo
Cloning into '.'...
The server's host key is not cached. You have no guarantee
that the server is the computer you think it is.
The server's ssh-ed25519 key fingerprint is:
ssh-ed25519 255 SHA256:36dhwOnTnvMgCfmPi2R//aNBncI9CdIPdpo0HoAi5e8
If you trust this host, enter "y" to add the key to
PuTTY's cache and carry on connecting.
If you want to carry on connecting just once, without
adding the key to the cache, enter "n".
If you do not trust this host, press Return to abandon the
connection.

Then it hangs waiting for Putty - which should not be used here...

• [ ] Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• [ ] Ensure that the pull request title represents the desired changelog entry
• [ ] Please describe what you did
• [ ] Link to relevant issues in GitHub or Jira
• [ ] Link to relevant pull requests, esp. upstream and downstream changes
• [ ] Ensure you have provided tests - that demonstrates feature works or fixes the issue

[jtnord]

also partially amends #900 as files should be written in the charset that the underlying system expects them to be in which may not be UTF-8

[jtnord]