run-tests: add flag to provide extra hgrc options for test runs

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.

graphlog: display nodes with more than 2 predecessors While nodes with more than 2 parents do not exist in revision graphs, they do appear when you transform them by removing subgraphs while trying to preserve ancestry links. This code was borrowed from Peter Arrenbrecht <peter.arrenbrecht@gmail.com> pbranch extension.

context: provide an efficient iterator for workingctx This avoids needing to call status or build a synthetic manifest.

merge with stable

merge with nicdumz

tests: export patches only once in test-impexp-branch

tests: do not export several times the same patch/diff in test-import