* Clean up ref name rules
Clean up checks on reference names to better conform to the guideline
here: https://git-scm.com/docs/git-check-ref-format
This fixes half of #6321
* Update branch create integration test
According to: https://git-scm.com/docs/git-check-ref-format
And: git check-ref-format "master/feature=test1"
This is a valid branch name and we should not be testing for it to fail.