Improve commit testing

[spenserblack]

There are several variations of commits (new file + changed file, changed file + untracked file, etc.) that can be tested.

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(This part of the issue might not be a "good first issue" in terms of easiness)

Also, the status of (expected) committed files should be checked. Need to research this, since the status of committed files seems to be "untracked" (byte('?')) instead of "unmodified" (byte(' ')).

[spenserblack]

Closing since this was written before major rewrite, and I need to revisit this project to see what needs to be done.