tests/test-status-committed-and-ignored.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.

#testcases dirstate-v1 dirstate-v2

#if dirstate-v2
  $ cat >> $HGRCPATH << EOF
  > [format]
  > use-dirstate-v2=1
  > [storage]
  > dirstate-v2.slow-path=allow
  > EOF
#endif

  $ rm -rf r

  $ hg init r
  $ cd r
  $ mkdir d1
  $ mkdir d2
  $ touch d1/f d2/f
  $ hg commit -Am '.'
  adding d1/f
  adding d2/f
  $ echo 'syntax:re' >> .hgignore
  $ echo '^d1$' >> .hgignore
  $ hg commit -Am "ignore d1"
  adding .hgignore

Now d1 is a directory that's both committed and ignored.
Untracked files in d2 are still shown, but ones in d1 are ignored:

  $ touch d1/g
  $ touch d2/g
  $ RAYON_NUM_THREADS=1 hg status
  ? d2/g