graphmod: attempt to clarify documentation of groupbranchiter() Thanks to Pierre-Yves for checking my cleanups here and helping me understand the algorithm well enough to help document it.

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.

graphlog: add a way to test the 'groupbranchiter' function We add an experimental config option to use the topological sorting. I first tried to hook the 'groupbranchiter' function in the 'sort' revset but this was useless because graphlog enforces revision number sorting :( As the goal is to advance on the topological iteration logic, I see this experimental option as a good way to move forward. We have to use turn the iterator into a list because the graphlog is apparently not ready for pure iterator input yet.

graphmod: add a function for topological iteration This changeset introduces a function to perform topological (one branch after the other) iteration over a set of changesets. This first version has a lot of limitations, but the approach should be flexible enough to allow many improvements in the future. This changeset aims to set the first stone more than providing a complete solution. The algorithm does not need to know the whole set of nodes involved before emitting revision. This makes it a good candidate for usage in place like `hg log` or graphical tools that need a fast first result time.

namespaces: add branches Note that the exception-catching from the previous branchtip check is moved up to catch exceptions from the try block surrounding the namespace lookup.