rebase: improve invalid revisions filtering - Filter rebasestate nullmerge and unrebased revision before considering updating obsolete. This simplifies the handling of obsolete and make it ignore unrebased revision rather than extinguishing them. - Apply obsolete markers only if rebasestate is not empty, testing rebasetarget was irrelevant.

test-evolve: extend output and exhibit an amend bug The extended section shows the parent revision stabilizing itself on another revision, without --any. In theory, only descendants of the parent predecessors or of its descendants should be stabilized, and be stabilized in parent subtree. Unfortunately, stabilize implementation correctly picks the changesets to stabilize but not their target. This problem is aggravated by amend registering too many obsolete markers which prevents the stabilize selection heuristic to prune several changesets.

evolve: remove --change . == --change .^ crazyness

evolve: use explicit phase constants

[doc] update readme

[doc] have people update on stable after cloning