copies: fix the changeset based algorithm regarding merge
In 99ebde4fec99, we changed the list of files stored into the files field.
This lead to the changeset centric copy algorithm to break in various merge
situation involving merge. Older information could reach the merge through
p1, and while information from p2 was strictly fresher, it would get
We update the situation with more details about which revision introduces rename
information. This help use making the right decision in case of merge.
We are now running a more comprehensive suite of test with include this kind of
situation. The behavior differ slightly from the filelog based in a couple of
instance. There is mostly two distinct cases:
- there are conflicting rename information in a merge (different rename history
on each side). In this case the filelog based implementation arbitrarily pick a
side based on the file-revision-number. So it depends on a local factor. The
changeset centric algorithm will use a deterministic approach, by picking the
information coming from the first parent of the merge. This is stable across
- rename information related to file that exist in both source and destination.
The filelog based implementation do not even try to detect these, however the
changeset centric one get them for "free" (it is simpler to detect them than
The new implementation focus on correctness. Performance improvement will come
Differential Revision: https://phab.mercurial-scm.org/D8244