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.