patch: stop modifying gitpatch objects gitpatch objects emitted by iterhunks() were referencing file paths unmodified from the input patch. _applydif() made them usable by modifying the gitpatch objects in-place with specified path strip level. The same modified objects were then reused by iterhunks() generator. _applydiff() now copies and update the paths which completely decouples both routines. As a side effect, the "git" event now receives only metadata about copies/renames to perform the necessary copies ahead of time. Other actions are handled in the "file" event.