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  • Pierre-Yves David's avatar
    copies: fix the changeset based algorithm regarding merge · 45f3f35cefe7
    Pierre-Yves David authored
    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
    overwritten anyway.
    
    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:
    
    1) 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
    different clone.
    
    2) 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
    not).
    
    The new implementation focus on correctness. Performance improvement will come
    later.
    
    Differential Revision: https://phab.mercurial-scm.org/D8244
    45f3f35cefe7