test: consolidate the content-divergent test cases This commit move most of the content divergent related test in dedicated and thematic test files.

changelog: mention the fix to issue6057

extensions: avoid enabling evolve for unrelated repositories (issue6057) The support for the `experimental.evolve` config have been there forever. So we can stop using the global variable. This help avoiding evolve to enable itself of repository that did not explicitly activated it. For example, this is useful for hgwebdir. Before this change, evolution feature had to be explicitly disabled or enabled in every single repository.

stack: improve set combination logic

stack: fix phasecache._phasesets check logic When _phasesets is not None, it's a list, and it contains set()s of revisions in a specific phase, starting from public, draft, secret and so on. But since repos are supposed to have the majority of revisions in public phase, the first element of this list is not a (potentially huge) set, but None. Previously this code tried to check if there's any element that is None, and was always finding None at index 0, so the short path was executed every time and the rest of the function was never used.

evolve: remove todo markers from a test which has been fixed

next: clarify tests related to `commands.update.check` test This clarify the test and help understand the next changeset.

stack: simplify phasecache checks in _stackcandidates()