tests/test-empty-manifest-index.t

dirstate: drop comparison primitive on the timestamp class

All comparison are now managed without using operator :

- the status mtime comparisons is handled by the DirstateItem,
- the fixup reliability check,
- the update "hack".

So we no longer needs the operator and should discourage its usage.

Differential Revision: https://phab.mercurial-scm.org/D11841

Test null revisions (node 0000000000000000000000000000000000000000, aka rev -1)
in various circumstances.

Make an empty repo:

  $ hg init a
  $ cd a

  $ hg files -r 0000000000000000000000000000000000000000
  [1]
  $ hg files -r .
  [1]

Add an empty commit (this makes the changelog refer to a null manifest node):


  $ hg commit -m "init" --config ui.allowemptycommit=true

  $ hg files -r .
  [1]

Strip that empty commit (this makes the changelog file empty, as opposed to missing):

  $ hg --config 'extensions.strip=' strip . > /dev/null

  $ hg files -r .
  [1]