tests/test-narrow-acl.t

revlog: add a C implementation of `headrevsdiff`

Python implementation of `headrevsdiff` can be very slow in the worst
case compared with the `heads` computation it replaces, since the
latter is done in C.

Even the average case of this Python implementation is still
noticeable in the profiles.

This patch makes the computation much much faster by doing it in C.

Make a narrow clone then archive it
  $ . "$TESTDIR/narrow-library.sh"

  $ hg init master
  $ cd master

  $ for x in `$TESTDIR/seq.py 3`; do
  >   echo $x > "f$x"
  >   hg add "f$x"
  >   hg commit -m "Add $x"
  > done
  $ cat >> .hg/hgrc << EOF
  > [narrowacl]
  > default.includes=f1 f2
  > EOF
  $ hg serve -a localhost -p $HGPORT1 -d --pid-file=hg.pid
  $ cat hg.pid >> "$DAEMON_PIDS"

  $ cd ..
  $ hg clone http://localhost:$HGPORT1 narrowclone1
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 2 changes to 2 files
  new changesets * (glob)
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

The clone directory should only contain f1 and f2
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  f2

Requirements should contain narrowhg
  $ hg debugrequires -R narrowclone1 | grep narrowhg
  narrowhg-experimental

NarrowHG should track f1 and f2
  $ hg -R narrowclone1 tracked
  I path:f1
  I path:f2

Narrow should not be able to widen to include f3
  $ hg -R narrowclone1 tracked --addinclude f3
  comparing with http://localhost:$HGPORT1/
  searching for changes
  abort: The following includes are not accessible for test: ['path:f3']
  [255]
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  f2
  $ hg -R narrowclone1 tracked
  I path:f1
  I path:f2

Narrow should allow widen to include f2
  $ hg -R narrowclone1 tracked --removeinclude f2 > /dev/null
  $ hg -R narrowclone1 tracked
  I path:f1
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  $ hg -R narrowclone1 tracked --addinclude f2
  comparing with http://localhost:$HGPORT1/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 0 changesets with 1 changes to 1 files
  $ hg -R narrowclone1 tracked
  I path:f1
  I path:f2
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  f2