relnotes: skip the test if the source repository is not readable The test want to run the relnot extension, with the tested mercurial, on the original repository. This is not always possible (e.g. when running with --pure and the repository use zstd for example). So we skip the test in this case.

check-code: document reason and suggest alternative to exit code negation The check was introduced in f48b075ff088. We trust the explanation from there.

ci: drop the HGMODULEPOLICY overwrite The test runner have been setting them properly for a while now. So we don't need to do it manually anymore.

test: preserve the existing module policy config for testrepohg resuse The test runner is, righfully, setting HGMODULEPOLICY to match the flavor requests to run the tests. However this mess with the `testrepohg` ability to run properly, as the newly set policy might be incompatible with its installation, or its ability to read the test repo. So we preserve the initial value in a dedicated variable and use it in the `testrepohg` helper.

module-policy: ignore empty module policy This make the variable easier to work with, the empty value is not ambiguous about not wanting to get in the way.

tests: provide an alternate fake lock for filesystems without symlink support

tests: disable `worker.backgroundclose` to stabilize a test on Windows TIL that `worker.enabled=0` doesn't prevent these workers from spinning up. At any rate, there's already a whole lot of conditionalized output following `cat client.log`, the placement of the "starting 4 threads for background file closing" message seems unstable, and we don't care about those worker threads here. Preventing the message is better for test maintenance.