fileset: add class to host special handling of initial subset
Future patches will add a function to switch mctx.ctx object so that we can
forcibly evaluate a fileset expression in a specified revision. For example,
new "revs()" function will be used to match predicate agains another revision
$ hg revert 'set:revs(42, added())'
fullmatchctx class is similar to revset.fullreposet. It will allow us to
recalculate the subset only if it is not filtered yet.
patchbomb: add config knob to generate flags by template (
issue5354)
This can be used to flag patches by branch or topic automatically. Flags
optionally given by --flag option are exported as {flags} template keyword,
so you can add --flag V2.