easily use meld 3-pane view to review merge commits?

I like how git-mergetool can use meld with 3 pane view to see merge conflicts:

  git mergetool --tool=meld

I'd like to use the same sort of view to see already-committed merges, but I didn't find an easy way to do it. It seems like git-diff, git-difftool and git-show are oriented entirely towards diff or 2-pane view rather than diff3/3-pane that git-mergetool uses. Did I miss the existing functionality somehow?

I asked about this on stackoverflow and made an answer with a script also:

  https://stackoverflow.com/questions/79599180/show-a-git-merge-commit-in-three-panel-form-inimeld

If there isn't any existing automatic way to inspect merge commits in this way I'd like to improve this script and turn it into git-meld3 or something. It's tempting to think it could be wedged into the existing diff-oriented architecture of git-diff/difftool/show but the result would probably be too confusing to be useful.

Britton