Summary:
Vendored using GPL2 license from https://bitbucket.org/marmoute/mutable-history
changeset c9f1118b33d60f8faa4b89988a8155c544f5bb0d without modification.
Test Plan: N/A. The code was imported as is.
Reviewers: #sourcecontrol, sid0
Reviewed By: sid0
Subscribers: mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D5142063
Signature: t1:5142063:1496173803:d0a9fa50a8423a531432ac3cff378b50952684b1
