tests/test-backwards-remove.t

notify: add option for deterministic message-id generation

Copied from email by durin42:
> Pierre-Yves asked offline why I asked a new option for this and why it
> is not the default. Message-Id is supposed to be unique world-wide and
> while it is desirable to have a deterministic mechanism for them for
> creating follow-up emails, it needs organisational control for ensuring
> the uniqueness.


Differential Revision: https://phab.mercurial-scm.org/D6824

  $ hg init
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ ls
  a
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ hg co 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

B should disappear

  $ ls
  a