git: add test showing `hg commit -i` working on a git repo Shows `hg commit -i` working on a git repo via the `git` extension. Adds working directory changes to files `alpha` and `beta`, then selects only `alpha` changes and commits them. As of now this would fail for a filename that includes uppercase characters due to the lack of case folding support in the extension. Differential Revision: https://phab.mercurial-scm.org/D9081