topic: only require obsolete support for --change

commit: add a --topic flag

topic: note when switching topics

summary: add topic summary hook

topics: add command summary

docs: fix format of extension docstring

constants: extract key for extra into a constant It might be prudent to prefix it, and regardless it was bugging me to have it repeated everywhere.

topic: add ability to change topic of non-public changes This is a little crude, but it gets the job done. You probably don't want to use this without evolution for now.

revset: add a topic() revset for querying topics

topic: disallow use of topics without obsolete enabled This is a prelude to allowing changing topics. The experience will be disastrous without obsolete markers, so let's just preempt any potential problems.

topic: use repo.set() where we need a changectx anyway I always forget repo.set() exists and use repo.revs(). Sigh.

testlib: enable rebase and obsolete for easier testing

Initial dumb version of topics.

serveronly: deduplicate code with the main evolve extension Now that 'serveonly' is a sub module of evolve. We can access its content in evolve. As a result we stop duplicating code all common parts are defined in the 'serveronly' module and imported by evolve when needed.