patch: extract fs access from patchfile into fsbackend Most filesystem calls are already isolated in patchfile but this is not enough: renames are performed before patchfile is available and some chmod calls are even done outside of the applydiff call. Once all these calls are extracted into a backend class, we can provide cleaner APIs to write to a working directory context directly into the repository.

mq: fix qpush changes detection of renamed files patch.changedfile() was not considering renamed file source as changed.