patch: add a workingbackend dirstate layer on top of fsbackend _updatedir() is no longer used by internalpatch() The change in test-mq-missingfiles.t comes from workingbackend not considering the missing 'b' file as changed, thus not calling addremove() on it.

patch: handle binary copies as regular ones This introduces a performance regression for large files, as they will be copied just to be clobbered afterwards since binary patching does not use deltas. But it simplifies the code and the previous optimization will be reintroduced later in a better way.

patch: remove files while patching, not in updatedir() At this point, updatedir() only reads the working directory and update the dirstate.

patch: set desired mode when patching, not in updatedir() This patch and the following aim at merging _updatedir() actions into _applydiff().