tests/test-narrow-debugcommands.t

scmutil: add option to register summary callbacks as transaction validators

We have a list of summary callbacks which are run after the transaction is
closed to show what has changed and what not. This patch makes it possible to
register those callbacks as transaction validators so that we can show summary
before committing the transaction and prompt user to accept the changes.

The goal of this is to implement `pull --confirm`.

Differential Revision: https://phab.mercurial-scm.org/D8199

  $ . "$TESTDIR/narrow-library.sh"
  $ hg init repo
  $ cd repo
  $ cat << EOF > .hg/store/narrowspec
  > [include]
  > path:foo
  > [exclude]
  > EOF
  $ cp .hg/store/narrowspec .hg/narrowspec.dirstate
  $ echo treemanifest >> .hg/requires
  $ echo narrowhg-experimental >> .hg/requires
  $ mkdir -p foo/bar
  $ echo b > foo/f
  $ echo c > foo/bar/f
  $ hg commit -Am hi
  adding foo/bar/f
  adding foo/f
  $ hg debugindex -m
     rev linkrev nodeid       p1           p2
       0       0 14a5d056d75a 000000000000 000000000000
  $ hg debugindex --dir foo
     rev linkrev nodeid       p1           p2
       0       0 e635c7857aef 000000000000 000000000000
  $ hg debugindex --dir foo/
     rev linkrev nodeid       p1           p2
       0       0 e635c7857aef 000000000000 000000000000
  $ hg debugindex --dir foo/bar
     rev linkrev nodeid       p1           p2
       0       0 e091d4224761 000000000000 000000000000
  $ hg debugindex --dir foo/bar/
     rev linkrev nodeid       p1           p2
       0       0 e091d4224761 000000000000 000000000000
  $ hg debugdata -m 0
  foo\x00e635c7857aef92ac761ce5741a99da159abbbb24t (esc)
  $ hg debugdata --dir foo 0
  bar\x00e091d42247613adff5d41b67f15fe7189ee97b39t (esc)
  f\x001e88685f5ddec574a34c70af492f95b6debc8741 (esc)
  $ hg debugdata --dir foo/ 0
  bar\x00e091d42247613adff5d41b67f15fe7189ee97b39t (esc)
  f\x001e88685f5ddec574a34c70af492f95b6debc8741 (esc)
  $ hg debugdata --dir foo/bar 0
  f\x00149da44f2a4e14f488b7bd4157945a9837408c00 (esc)
  $ hg debugdata --dir foo/bar/ 0
  f\x00149da44f2a4e14f488b7bd4157945a9837408c00 (esc)