copies-rust: refactor the "deletion" case We rearrange the code to single out the case where information need to be overwritten on both side of the merge. This open the way to better dealing with this case. Differential Revision: https://phab.mercurial-scm.org/D9651

copies-rust: process copy information of both parent at the same time This avoid a double iteration and this open the way to a better handing of deletion. That better handling of deletion is the core reason we are doing this refactoring. Differential Revision: https://phab.mercurial-scm.org/D9650

copies-rust: yield both p1 and p2 copies in `ChangedFiles.actions()` Instead of filtering the relevant parent inside de ChangedFiles method, we now yield all copies information and let the caller do the filtering. Soon, the filtering will be replaced by dispatching. Differential Revision: https://phab.mercurial-scm.org/D9649

copies-rust: extract the processing of a single copy information This will make it easy to process copy from both p1 and p2 in the same `add_from_changes` call. Differential Revision: https://phab.mercurial-scm.org/D9648

copies-rust: use matching to select the final copies information This is a bit more idiomatic and this prepare a future refactoring where InternalCopies from both parent would be updated at the same time. Differential Revision: https://phab.mercurial-scm.org/D9647

copies-rust: get the parents' copies earlier This remove some conditional nesting and prepare for future work were we will unify the handling of copies from p1 and p2. Differential Revision: https://phab.mercurial-scm.org/D9646

copies-rust: remove the ancestor Oracle logic We are not doing any `is_ancestor` call anymore. So we can drop that logic and associated arguments. Differential Revision: https://phab.mercurial-scm.org/D9645