tests/test-abort-checkin.t

clfilter: add a propertycache that must be unfiltered

Some of the localrepo property caches must be computed unfiltered and
stored globally. Some others must see the filtered version and store data
relative to the current filtering.

This changeset introduces two classes `unfilteredpropertycache`
and `filteredpropertycache` for this purpose. A new function
`hasunfilteredcache` is introduced for unambiguous checking for cached
values on unfiltered repos.

A few tweaks are made to the property cache class to allow overriding
the way the computed value is stored on the object.

Some logic relative to _tagcaches is cleaned up in the process.

  $ cat > abortcommit.py <<EOF
  > from mercurial import util
  > def hook(**args):
  >     raise util.Abort("no commits allowed")
  > def reposetup(ui, repo):
  >     repo.ui.setconfig("hooks", "pretxncommit.nocommits", hook)
  > EOF
  $ abspath=`pwd`/abortcommit.py

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH
  $ echo "abortcommit = $abspath" >> $HGRCPATH

  $ hg init foo
  $ cd foo
  $ echo foo > foo
  $ hg add foo

mq may keep a reference to the repository so __del__ will not be
called and .hg/journal.dirstate will not be deleted:

  $ hg ci -m foo
  error: pretxncommit.nocommits hook failed: no commits allowed
  transaction abort!
  rollback completed
  abort: no commits allowed
  [255]
  $ hg ci -m foo
  error: pretxncommit.nocommits hook failed: no commits allowed
  transaction abort!
  rollback completed
  abort: no commits allowed
  [255]

  $ cd ..