test: avoid 'test-check-commit.t' complaining copied code We switch to git diff.

topic: small test cleanuo The section was repeated.

topic: move the heads data to the branch line when appropriates The topic line is dropped as it is quite confusing.

topic: add some initial support for using stack on named branch Stack is a useful command that can make sense in other context. The current support is hacky and awful, but we have something!

topic: explicitly pass topic as a keyword argument This clarify all callers before adding more logic related to bare branch in stack.

topic: makes split keep the topic Refactor split to extract the preparation of the working directory in a separate function. This helps topic wrap this function to save topic before update and restore it after preparing the working directory just before the split.

topic: add tests for fold behavior with topics Clarify the fold behavior for keeping topics.

topics: pass quietempty=True to suppress useless output while changing topics This will help in suppressing the output "0 files updated, 0 file removed, ..."

topics: return early so that other if conditions don't get execute (issue5600) We were not returning after the _changetopics() call and hence the if's below it were also executed which resulted in changing of current topic. This prevent current topic to be updated even when we only affect changeset unrelated to the working copy. Not that the rebase output change as it expose a new bug (rebased changeset gain a topic)

test: extra output to understand the next changeset better