I'll have the same concern on all git changes. Pants until now has tried to use an Scm - not a Git. I'd like to continue to keep the abstraction when it makes sense. Here it does - all of svn, hg, git support getting the date of a `commit_id`. If you can lift up a method + pydoc and keep the terminology consistent that would be best.
As a whitebox test this works, but as a blackbox commit_date could just be doing a rev-parse and still passing. I'm conflicted, but it might be nice to define the API as returning a python date structure forcing the impls to parse the date. Just talking out loud. I'll patch this in as-is.