tests/test-requires.t

obsolete: explicitly track folds inside the markers

We now record information to be able to recognize "fold" event from
obsolescence markers. To do so, we track the following pieces of information:

a) a fold ID. Unique to that fold (per successor),
b) the number of predecessors,
c) the index of the predecessor in that fold.

We will now be able to create an algorithm able to find "predecessorssets".

We now store this data in the generic "metadata" field of the markers.
Updating the format to have a more compact storage for this would be useful.

This way of tracking a fold through multiple markers could be applied to split
too. This would have two advantages:

1) We get a simpler format, since number of successors is limited to [0-1].
2) We can better deal with situations where only some of the split successors
   are pushed to a remote repository.

We should look into the relevance of such a change before updating the on-disk
format.

note: unlike splits, folds do not have to deal with cases where only some of
the markers have been synchronized. As they all share the same successor
changesets, they are all relevant to the same nodes.

  $ hg init t
  $ cd t
  $ echo a > a
  $ hg add a
  $ hg commit -m test
  $ rm .hg/requires
  $ hg tip
  abort: unknown version (2) in revlog 00changelog.i!
  [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 __future__ import absolute_import
  > from mercurial import extensions, localrepo
  > def featuresetup(ui, supported):
  >     for name, module in extensions.extensions(ui):
  >         if __name__ == module.__name__:
  >             # support specific feature locally
  >             supported |= {'featuresetup-test'}
  >             return
  > def uisetup(ui):
  >     localrepo.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 ..