graphmod: rename graph-topological config to graph-group-branches The latter suggests what the change is slightly better.

groupbranchiter: allow callers to select the first branch Instead of just bootstrapping the algorithm with the first revision we see, allow callers to pass revs that should be displayed first. All branches are retained until we can display such revision. Expected usage is to display the current working copy parent first.

groupbranchiter: support for non-contiguous revsets The algorithm now works when some revisions are skipped. We now use "first included ancestors" instead of just "parent" to link changesets with each other.

groubranchhiter: indent most of the inner code We are going to add an additional layer of indentation to support non-contiguous revset. We do it in a pure code movement changeset to help the readability of the next changeset.