tests/test-check-execute.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 test-repo execbit

  $ . "$TESTDIR/helpers-testrepo.sh"
  $ cd "`dirname "$TESTDIR"`"

look for python scripts without the execute bit

  $ testrepohg files 'set:**.py and not exec() and grep(r"^#!.*?python")'
  [1]

look for python scripts with execute bit but not shebang

  $ testrepohg files 'set:**.py and exec() and not grep(r"^#!.*?python")'
  [1]

look for shell scripts with execute bit but not shebang

  $ testrepohg files 'set:**.sh and exec() and not grep(r"^#!.*(ba)?sh")'
  [1]

look for non scripts with no shebang

  $ testrepohg files 'set:exec() and not **.sh and not **.py and not grep(r"^#!")'
  [1]