tests/test-requires.t

parsers: optimize filtered headrevs logic

The old native head revs logic would iterate over every node, starting from 0,
and check if every node was filtered (by testing it against the filteredrevs
python set). On large repos with hundreds of thousands of commits, this could
take 150ms.

This new logic iterates over the nodes in reverse order, and skips the filtered
check if we've seen an unfiltered child of the node. This saves approximately a
bagillion filteredrevs set checks, which shaves the time down from 150ms to
20ms during every branch cache write.

  $ hg init t
  $ cd t
  $ echo a > a
  $ hg add a
  $ hg commit -m test
  $ rm .hg/requires
  $ hg tip
  abort: index 00changelog.i unknown format 2!
  [255]
  $ echo indoor-pool > .hg/requires
  $ hg tip
  abort: repository requires features unknown to this Mercurial: indoor-pool!
  (see https://mercurial-scm.org/wiki/MissingRequirement for more information)
  [255]
  $ echo outdoor-pool >> .hg/requires
  $ hg tip
  abort: repository requires features unknown to this Mercurial: indoor-pool outdoor-pool!
  (see https://mercurial-scm.org/wiki/MissingRequirement for more information)
  [255]
  $ cd ..

Test checking between features supported locally and ones required in
another repository of push/pull/clone on localhost:

  $ mkdir supported-locally
  $ cd supported-locally

  $ hg init supported
  $ echo a > supported/a
  $ hg -R supported commit -Am '#0 at supported'
  adding a

  $ echo 'featuresetup-test' >> supported/.hg/requires
  $ cat > $TESTTMP/supported-locally/supportlocally.py <<EOF
  > from mercurial import localrepo, extensions
  > def featuresetup(ui, supported):
  >     for name, module in extensions.extensions(ui):
  >         if __name__ == module.__name__:
  >             # support specific feature locally
  >             supported |= set(['featuresetup-test'])
  >             return
  > def uisetup(ui):
  >     localrepo.localrepository.featuresetupfuncs.add(featuresetup)
  > EOF
  $ cat > supported/.hg/hgrc <<EOF
  > [extensions]
  > # enable extension locally
  > supportlocally = $TESTTMP/supported-locally/supportlocally.py
  > EOF
  $ hg -R supported status

  $ hg init push-dst
  $ hg -R supported push push-dst
  pushing to push-dst
  abort: required features are not supported in the destination: featuresetup-test
  [255]

  $ hg init pull-src
  $ hg -R pull-src pull supported
  pulling from supported
  abort: required features are not supported in the destination: featuresetup-test
  [255]

  $ hg clone supported clone-dst
  abort: repository requires features unknown to this Mercurial: featuresetup-test!
  (see https://mercurial-scm.org/wiki/MissingRequirement for more information)
  [255]
  $ hg clone --pull supported clone-dst
  abort: required features are not supported in the destination: featuresetup-test
  [255]

  $ cd ..