tests/test-revlog-packentry.t

notify: optional mail threading based on obsmarker

When notify.reply is set and a changeset has a predecessor in the
repository, include In-Reply-To pointing to the message-id that would
have been generated for the oldest predecessor. This allows mail
threading like Phabricator for common cases like rebasing changes, but
will be optimal for cases like folding.

Differential Revision: https://phab.mercurial-scm.org/D8172

  $ hg init repo
  $ cd repo

  $ touch foo
  $ hg ci -Am 'add foo'
  adding foo

  $ hg up -C null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

this should be stored as a delta against rev 0

  $ echo foo bar baz > foo
  $ hg ci -Am 'add foo again'
  adding foo
  created new head

  $ hg debugindex foo
     rev linkrev nodeid       p1           p2
       0       0 b80de5d13875 000000000000 000000000000
       1       1 0376abec49b8 000000000000 000000000000

  $ cd ..