tests/test-update-issue1456.t

match: teach diffmatcher.visitdir() to return 'all' if possible

This patch teaches differencematcher.visitdir() to return 'all' when
m1.visitdir() returns 'all' and m2 does not matches.

Before this patch, from a differencematcher.visitdir(), we always returned
either True or False. We never returned 'all' even when we can. This causes
problem when m1 and m2 of a differencematcher are themselves differencematcher.
In that case, we try to check:

`if self._m2_.visitdir(dir) == 'all'`

which will never be 'all' even though it can be.

This leads to iterating over a lot of sub-directory manifest, even though we
don't want to while extending a narrow clone. I am yet to measure the impact of
this but calculating manifest was taking ~50-60 seconds, so this should
definitely save some of time there.

Differential Revision: https://phab.mercurial-scm.org/D5814

#require execbit

  $ rm -rf a
  $ hg init a
  $ cd a

  $ echo foo > foo
  $ hg ci -qAm0
  $ echo toremove > toremove
  $ echo todelete > todelete
  $ chmod +x foo toremove todelete
  $ hg ci -qAm1

Test that local removed/deleted, remote removed works with flags
  $ hg rm toremove
  $ rm todelete
  $ hg co -q 0

  $ echo dirty > foo
  $ hg up -c
  abort: uncommitted changes
  [255]
  $ hg up -q
  $ cat foo
  dirty
  $ hg st -A
  M foo
  C todelete
  C toremove

Validate update of standalone execute bit change:

  $ hg up -C 0
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ chmod -x foo
  $ hg ci -m removeexec
  nothing changed
  [1]
  $ hg up -C 0
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg up
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg st

  $ cd ..