Summary: creating a mercurial extension so that `hg record` functionality can be used via a text editor (instead of interactive command prompt or curses menu)
Test Plan: `$ run-tests.py test-edrecord.t`
Reviewers: durham, skreyen, most, #sourcecontrol, asriram, simonfar
Reviewed By: simonfar
Subscribers: quark, rmcelroy, simonfar, mjpieters, #nuclide
Differential Revision: https://phabricator.intern.facebook.com/D4547080
Tasks: 15728734
Signature: t1:4547080:1487842609:8855e35010cac3b6d2b136a80d7effa369eb1da8
