fileset: make debugfileset filter repository files
This prepares for the structural change of the fileset. A computed fileset
will no longer be a set of files, but a boolean function (i.e. matcher) to
test if an input file matches the given fileset expression.
--all-files option is added because some examples in the test need to scan
files across revisions.
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.