RFR: 2588: Auto Labeling should ignore merge commits

[Erik Joelsson]

On Wed, 17 Sep 2025 20:08:33 GMT, Erik Joelsson <erikj at openjdk.org> wrote:

> I think I have figured out a better algorithm, but I'm not sure yet:

I did some more thinking and I think I have a much simpler proposal (as I already shared in person, but writing it here for transparency).

Instead of creating diffs between series of commits in the PR branch, we should always just diff against the merge-base with the target branch. The first auto labeling is the base case, where we just do exactly this and add labels based on the changed files. Then for additional labeling, we first repeat the diff from the previous run, then we create the diff from the current PR head to its merge-base. This gives us two sets of changed files. We subtract the set from the previous labeling from the set from the current PR head and calculate additional labels from that.

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PR Comment: https://git.openjdk.org/skara/pull/1740#issuecomment-3304492180