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.

patchbomb: pass around ui and revs that are needed for flag template See the next patch for why.