IIRC vscode with gitlens extension shows blame on hover, also for the conflicting lines.
I really hate that relative terminology. Call them "working copy", "merging commit" and "common ancestor" or something similarly absolute. And give me the revision/commit id's for each, so it's crystal clear in case I want to check up manually.
Not a dig on the vscode extension, but 3-way diff tools in general.
> And give me the revision/commit id's for each
It could show the branch names! `change on master`, `change on myfeature` or whatever.