D3854: rebase: add lock to cover whole dryrun process

[yuja (Yuya Nishihara)]

yuja added a comment.


  Rebased on top of https://phab.mercurial-scm.org/rHG2394cd58b81f77816caf4068ed5e441089460b47 and queued, thanks.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D3854

To: khanchi97, #hg-reviewers
Cc: yuja, mercurial-devel