D821: unamend: move fb extension unamend to core

[durham (Durham Goode)]

durham added inline comments.

INLINE COMMENTS

> uncommit.py:260
> +
> +        tr = repo.transaction('unamend')
> +        with dirstate.parentchange():

This should be in a with statement probably?  Can we just have it be as part of the top level lock with statement?

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D821

To: pulkit, #hg-reviewers
Cc: durham, mercurial-devel