Make it possible to disable filtering for a pattern.
Rationale: Apparently there were no way to disable for example win32text extension locally.
RFC: Can it already be done another way?
adding foo
updating working directory
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% should fail
pulling from ../tt
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
not updating, since new heads added
(run 'hg heads' to see heads, 'hg merge' to merge)
% should fail
pulling from ../t
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
not updating, since new heads added
(run 'hg heads' to see heads, 'hg merge' to merge)
merging foo
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% should work
pulling from ../tt
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (-1 heads)
1 files updated, 0 files merged, 0 files removed, 0 files unresolved