tests/test-absorb-unfinished.t

rust-matchers: fix quadratic complexity in `FileMatcher`

Concretely, this command:

```
$ echo hg up -r <nodeid>; time hg revert dir1 dir2 -r <othernode> --debug
hg up -r <nodeid>

real	0m14.690s
user	0m14.766s
sys	0m5.430s
```

was much slower despite using 16 cores before this change.
The approach taken here is the same one used in match.py, in exactmatcher.

This changeset was originally written by Valentin Gatien-Baron in a private
repository.
I have redacted the commit message and did a minor clean up of the code.

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > absorb=
  > EOF

Abort absorb if there is an unfinished operation.

  $ hg init abortunresolved
  $ cd abortunresolved

  $ echo "foo1" > foo.whole
  $ hg commit -Aqm "foo 1"

  $ hg update null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo "foo2" > foo.whole
  $ hg commit -Aqm "foo 2"

  $ hg --config extensions.rebase= rebase -r 1 -d 0
  rebasing 1:c3b6dc0e177a tip "foo 2"
  merging foo.whole
  warning: conflicts while merging foo.whole! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see 'hg resolve', then 'hg rebase --continue')
  [240]

  $ hg --config extensions.rebase= absorb
  abort: rebase in progress
  (use 'hg rebase --continue', 'hg rebase --abort', or 'hg rebase --stop')
  [20]