graphlog: always sort revisions topologically The grapher cannot really handled revisions if they are not emitted in topological order. The previous 'reverse()' revset was not enough to achieve that and was replaced by an explicit sort call for simplicity. The --limit option is now also handled as usual with cmdutil.loglimit() instead of a 'limit' revset.

graphlog: take the union of --rev specs instead of the intersection

graphmod: correctly emit nodes with more than 2 predecessors The grandparent() function was returning only the closest predecessor of a missing parent while it must return all of them to display a correct ancestry graph.