Summary:
As discussed before, we think terms like "changeset" is more official to hg,
while less known as "commit" is used more widely.
This extension replaces "changeset" with "commit" so users will get a
consistent view about the term being used, and we can use "changeset" in our
code to be more official while don't need to worry about user friendliness.
Test Plan: Run the newly added test
Reviewers: #sourcecontrol, rmcelroy
Reviewed By: rmcelroy
Subscribers: rmcelroy, mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D3900240
Signature: t1:3900240:1474470482:44ac6e09d58e624c539bb1336842ce8911c9dcee
