Summary:
It's just copy-paste from my mutable-history patch series that ended up as
persistent hotfix.
The wrapping logic is very simple: it redirects '--fold' calls to original
metaedit and handles all the rest.
Test Plan:
Included a big copy-pase from test-evolve.t preserving only cases that were
executing metaedit and modified for the smaller test repo (the metaedit tests
were at the end of evolve test file).
Reviewers: #sourcecontrol, quark, simonfar
Reviewed By: quark, simonfar
Subscribers: rmcelroy, quark, mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D4708017
Signature: t1:4708017:1489524494:d682aab857e8422bb1a23adc22dddfb9f505b6b3
