tests: add extension to emulate invoking dirstate.write at the specific time This extension fakes 'now' for 'parsers.pack_dirstate()' to emulate invoking 'dirstate.write()' at the specific time, only when 'dirstate.write()' is invoked via functions below: - 'workingctx._checklookup()' (= 'repo.status()') - 'committablectx.markcommitted()' This is useful to reproduce timing critical issues fixed in subsequent patches.

convert: handle copies when converting from Perforce (issue4744)