tests/test-abort-checkin.t

tests: demonstrate a problem with renames on the p2 side of a conversion

I think this is related to the octopus merge being sloppy, and that's having a
cascading affect on the fixup merge.  If this change is made on p1 (specifically
with the 'Added parent file' commit), the failure doesn't occur.

The file modification with the rename doesn't seem to be necessary, but it's
what's happening in a production repo where I first noticed, so I left it.  This
is an example of the manifest divergence I'd been seeing, which wasn't fixed by
Yuya's recent changes.  This is separate from the changelog divergence I was
also seeing[1].  Probably nobody cares about bzr anymore, but this will also
affect git, since the octopus fixup code is in the hg sink.

[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2018-August/120473.html

  $ cat > abortcommit.py <<EOF
  > from mercurial import error
  > def hook(**args):
  >     raise error.Abort(b"no commits allowed")
  > def reposetup(ui, repo):
  >     repo.ui.setconfig(b"hooks", b"pretxncommit.nocommits", hook)
  > EOF
  $ abspath=`pwd`/abortcommit.py

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > mq =
  > abortcommit = $abspath
  > EOF

  $ hg init foo
  $ cd foo
  $ echo foo > foo
  $ hg add foo

mq may keep a reference to the repository so __del__ will not be
called and .hg/journal.dirstate will not be deleted:

  $ hg ci -m foo
  error: pretxncommit.nocommits hook failed: no commits allowed
  transaction abort!
  rollback completed
  abort: no commits allowed
  [255]
  $ hg ci -m foo
  error: pretxncommit.nocommits hook failed: no commits allowed
  transaction abort!
  rollback completed
  abort: no commits allowed
  [255]

  $ cd ..