tests: convert some 'hghave no-outer-repo' to #if In some places we instead use 'hg init' to create a well-known outer repo without any special extensions or other config settings.

strip: incrementally update the branchheads cache after a strip This function augments strip to incrementally update the branchheads cache rather than recompute it from scratch. This speeds up the performance of strip and rebase on repos with long history. The performance optimization only happens if the revisions stripped are all on the same branch and the parents of the stripped revisions are also on that same branch. This adds a few test cases, particularly one that reproduces the extra heads that mpm observed.

localrepo: convert _updatebranchcache from nodespace to revspace _updatebranchcache used to use revlog.reachable. After the switch to revlog.ancestors, we can now clean it up a bit and switch the algorithm from nodes to revs.

discovery: convert legacy part of checkheads to revs from nodes After a recent switch from revlog.reachable to revlog.ancestors, clean up this old call site, switching it from nodes to revs.

transplant: convert applied() algorithm from nodes to revs After a recent switch from revlog.reachable to revlog.ancestors, clean up the code a bit to use revs rather than nodes.

revlog: remove reachable and switch call sites to ancestors This change does a trivial conversion of callsites to ancestors. Followon diffs will switch the callsites over to revs.