Merge.

test-topic-dest: test fixes I should have put in the previous change I split a bigger change from marmoute that included some rebase support that I wanted to discuss more, but I didn't correctly commit my fixes to the tests before pushing. Oops.

topic: fix changing topics of commits that have an amend_source Includes a test for this specific case, but we should probably spend more time squinting at the interactions between the current topic wrapper function and commitctx for memctx instances.

topic: remove useless call to c.parents()

topic: fix up change logic a little and add debug logging

merge: use topic to pick default destination If the topic have multiple heads, reduce that. Otherwise, pick the branch we are on.

topic: introduce a 'ngtip' concept The concept is to be massively used in naming and default destination logic. The name is horrible so that people find a better one.

template: test that topic is accessible through template This comes free with the namespace feature but it is good to have.

test: adapt to newer mercurial

patch: import topic from patch header If the used Mercurial supports it, we import topic from patch headers.

patch: add topic to exported patch If used Mercurial supports it, we add a topic header to patches.

topic: work around stringmatcher moving during development of hg 3.6