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.
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL