I don't think that using filepath for a pattern is a good idea. Also, the tests are failing.

I would use the pattern option and when used the filepath should be ignored. @mojavelinux
What do you think?

In canonical git, the primary argument to git add (and similar commands) is called a pathspec. And a pathspec does accept wildcard characters.

If we are concerned about a breaking change, we could consider introducing pathspec as an alternative to filepath. That would a) align with canonical git and b) not impact any existing users.

I think if we are going to support wildcards, we should consider using a pattern matching library rather than trying to implement the logic within isomorphic-git. Though, there are benefits of doing it without an additional dependency.