tests/test-requires.t

templatekw: choose {latesttag} by len(changes), not date (issue5659)

As Augie reported in the bug, the current heuristic of choosing the
best tag of a merge commit by taking the one with newest tag (in terms
of tagging date) currently fails in the Mercurial repo itself. Copying
the example from Yuya:

  $ hg glog -T '{node|short} {latesttag}+{latesttagdistance}\n' \
    -r '4.2.3: & (merge() + parents(merge()) + tag())'
  o    02a745c20121 4.2.3+5
  |\
  | o    86aca74a063b 4.2.3+4
  | |\
  | | o  e6d8ee3c9ec3 4.3-rc+109
  | | |
  | | ~
  o |  a3ce07e2dde5 4.3.1+2
  : |
  o |  3fee7f7d2da0 4.3.1+0
  |/
  o    98e990bb7330 4.2.3+3
  |\
  | ~
  o  506d7e48fbe6 4.2.3+2
  :
  o  943c91326b23 4.2.3+0
  |
  ~

It seems to me like the best choice is the tag with the smallest
number of changes since it (across all paths, not the longest single
path). So that's what this patch does, even though it's
costly. Best-of-5 timings for Yuya's command above shows a slowdown
from 1.293s to 1.610s. We can optimize it later.

Differential Revision: https://phab.mercurial-scm.org/D447

  $ 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 mercurial import localrepo, extensions
  > 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.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 ..