tests/test-manifest.t

match: add visitchildrenset complement to visitdir

`visitdir(d)` lets a caller query whether the directory is part of the matcher.
It can receive a response of 'all' (yes, and all children, you can stop calling
visitdir now), False (no, and no children either), or True (yes, either
something in this directory or a child is part of the matcher).

`visitchildrenset(d)` augments that by instead of returning True, it returns a
list of items to actually investigate.  With this, code can be modified from:

    for f in self.all_items:
        if match.visitdir(self.dir + '/' + f):
            <do stuff>

to be:

    for f in self.all_items.intersect(match.visitchildrenset(self.dir)):
        <do stuff>

use of this function can provide significant performance improvements,
especially when using narrow (so that the matcher is much smaller than the stuff
we see on disk) and/or treemanifests (so that we can avoid loading manifests for
trees that aren't part of the matcher).

Differential Revision: https://phab.mercurial-scm.org/D4130

Source bundle was generated with the following script:

# hg init
# echo a > a
# ln -s a l
# hg ci -Ama -d'0 0'
# mkdir b
# echo a > b/a
# chmod +x b/a
# hg ci -Amb -d'1 0'

  $ hg init
  $ hg unbundle "$TESTDIR/bundles/test-manifest.hg"
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 3 changes to 3 files
  new changesets b73562a03cfe:5bdc995175ba
  (run 'hg update' to get a working copy)

The next call is expected to return nothing:

  $ hg manifest

  $ hg co
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg manifest
  a
  b/a
  l

  $ hg files -vr .
           2   a
           2 x b/a
           1 l l
  $ hg files -r . -X b
  a
  l
  $ hg files -T '{path} {size} {flags}\n'
  a 2 
  b/a 2 x
  l 1 l
  $ hg files -T '{path} {node|shortest}\n' -r.
  a 5bdc
  b/a 5bdc
  l 5bdc

  $ hg manifest -v
  644   a
  755 * b/a
  644 @ l
  $ hg manifest -T '{path} {rev}\n'
  a 1
  b/a 1
  l 1

  $ hg manifest --debug
  b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644   a
  b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 755 * b/a
  047b75c6d7a3ef6a2243bd0e99f94f6ea6683597 644 @ l

  $ hg manifest -r 0
  a
  l

  $ hg manifest -r 1
  a
  b/a
  l

  $ hg manifest -r tip
  a
  b/a
  l

  $ hg manifest tip
  a
  b/a
  l

  $ hg manifest --all
  a
  b/a
  l

The next two calls are expected to abort:

  $ hg manifest -r 2
  abort: unknown revision '2'!
  [255]

  $ hg manifest -r tip tip
  abort: please specify just one revision
  [255]