diff3 v0.3 Release Notes

  • 0.3 includes two semantic changes from @sth:

    Made conflicts shorter

    Conflicts sometimes include more elements than necessary:

    GHCi> diff3 "14567" "1234567" "1567"
    [Unchanged "1",Conflict "456" "23456" "56",Unchanged "7"]

    56 shouldn't be included in the conflict.

    ๐Ÿ›  This patch fixes the issue by only including additional elements for the diff that is "behind", instead of both diffs. It advances only the minimal amount ๐Ÿ”€ necessary to bring both diffs in sync when searching for the end of a conflict.

    This way less items are included in the conflict:

    GHCi> diff3 "14567" "1234567" "1567"
    [Unchanged "1",Conflict "4" "234" "",Unchanged "567"]

    Made motion calculation consistent

    The motion function in shortestConflict counts how many elements of the first sequence are in a part of a diff. The function incurMotion then tries to advance by that many elements, but counts elements in the second sequence of the diff.

    This leads to inconsistent/wrong diffs:

    GHCi> diff3 "145" "12345" "1245"
    [Unchanged "1",Conflict "" "23" "24",Unchanged "4",LeftChange "5"]

    Here 4 is mentioned in the conflict as well as afterwards as unchanged. The training LeftChange 5 is really unchanged.

    With swapped arguments:

    GHCi> diff3 "1245" "12345" "145"
    [Unchanged "1",Conflict "24" "234" "",Unchanged "5",RightChange "5"]

    Here 4 is (unnecessarily) incorporated in the conflict and 5 is mentioned twice.

    ๐Ÿ›  This pull request fixes the counting in incurMotion, correcting the above examples:

    GHCi> diff3 "1245" "12345" "145"
    [Unchanged "1",Conflict "2" "23" "",Unchanged "45"]
    GHCi> diff3 "145" "12345" "1245"
    [Unchanged "1",Conflict "" "23" "2",Unchanged "45"]