I have a use case where credentials used in Git URLs need to be masked when written to the build log. Is this functionality something that would be accepted? I’d like to post a PR to add it. 
It depends on how you implement it. The git client plugin contributing guide says:
Before submitting your change, please assure that you’ve added tests which verify your change. There have been many developers involved in the git client plugin and there are many, many users who depend on the git client plugin. Tests help us assure that we’re delivering a reliable plugin, and that we’ve communicated our intent to other developers as executable descriptions of plugin behavior.
The most common reason for initial rejection of pull requests to the git plugin and git client plugin is for lack of automated tests. If you don’t provide tests, it will be rejected.
That makes sense. Thanks!
I’ll get a PR ready and submit. 