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.

syntax: re
/figures/[^/]+\.png$
^docs/build/
^docs/html/
^html/
\.pyc$
~$
\.orig$
\.rej$
\.err$