tests/test-merge-subrepos.t

graphlog: paths/-I/-X handling requires a new revset

The filtering logic of match objects cannot be reproduced with the existing
revsets as it operates at changeset files level. A changeset touching "a" and
"b" is matched by "-I a -X b" but not by "file(a) and not file(b)".

To solve this, a new internal "_matchfiles(...)" revset is introduced. It works
like "file(x)" but accepts more than one argument and its arguments are
prefixed with "p:", "i:" and "x:" to be used as patterns, include patterns or
exclude patterns respectively.

The _matchfiles revset is kept private for now:
- There are probably smarter ways to pass the arguments in a user-friendly way
- A "rev:" argument is likely appear at some point to emulate log command
  behaviour with regard to filesets: they are evaluated for the parent revision
  and applied everywhere instead of being reevaluated for each revision.

  $ hg init

  $ echo a > a
  $ hg ci -qAm 'add a'

  $ hg init subrepo
  $ echo 'subrepo = http://example.net/libfoo' > .hgsub
  $ hg ci -qAm 'added subrepo'

  $ hg up -qC 0
  $ echo ax > a
  $ hg ci -m 'changed a'
  created new head

  $ hg up -qC 1
  $ cd subrepo
  $ echo b > b
  $ hg add b
  $ cd ..

Should fail, since there are added files to subrepo:

  $ hg merge
  abort: outstanding uncommitted changes in subrepository 'subrepo'
  [255]