D4824: narrow: move support for `hg verify` into core

[indygreg (Gregory Szorc)]

indygreg added inline comments.

INLINE COMMENTS

> verify.py:39
>      # extension will pass in a matcher here.
>      def __init__(self, repo, match=None):
>          self.repo = repo.unfiltered()

`match` is unused after this change. Should we drop it?

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D4824

To: martinvonz, durin42, #hg-reviewers
Cc: indygreg, mercurial-devel