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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.

    🛠 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 🔀 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.

    🛠 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"]