The easiest thing to do would be to diff the results of your conflict resolution with a merge that auto-resolves conflicts without human intervention. Any automatic resolutions will be ignored, since they will be resolved in exactly the same way.
I see two ways of visualizing the possible “evil” resolutions. If you are making this into a script add
&> /dev/null to the end of all lines that you do not care to see output.
1) Use two separate diffs, one that favors the first parent, and a second that favors the second parent.
MERGE_COMMIT=<Merge Commit> git checkout $MERGE_COMMIT~ git merge --no-ff --no-edit -s recursive -Xours $MERGE_COMMIT^2 echo "Favor ours" git diff HEAD..$MERGE_COMMIT git checkout $MERGE_COMMIT~ git merge --no-ff --no-edit -s recursive -Xtheirs $MERGE_COMMIT^2 echo "Favor theirs" git diff HEAD..$MERGE_COMMIT
2) Diff against the results of the conflicted merge with the conflicts still in.
MERGE_COMMIT=<Merge Commit> git checkout $MERGE_COMMIT~ git -c merge.conflictstyle=diff3 merge --no-ff $MERGE_COMMIT^2 --no-commit git add $(git status -s | cut -c 3-) git commit --no-edit git diff HEAD..$MERGE_COMMIT