perf: fallback to subset if ondisk cache is missing in perfbranchmapload If there is no branchmap on disk for that filter, it means that the cache from some subset's filter is relevant for this one. We look for it instead of aborting. That way it is much simpler to run the command in an automated way. We can now add it to `test-contrib-perf.t`.

perf: prewarm the branchmap in perfbranchmapload It is not very interesting to have the command randomly failing because the branchmap for the tested filter happens to be cold. So we make sure to have a valid up to date branchmap before going further. The data might still be missing from disk if a subset was equivalent. See next changeset for details and fix.

localrepo: correct docstring of filectx() The same reason as b6c2543e1dd8. It can't be any changeset specifiers but revision number.

annotate: remove dead code to not convert path to relative path It's annotate. There should be at least one file path specified.

annotate: start pager soon after command options are validated It helps extracting helper class.

annotate: check and update command options first It helps extracting helper class.

annotate: format local tables in less-dense form I'll move these to a class, where one-extra indent will be needed.