RFH - git-log variant that _does_ search through diffs

[Surely this has been address before,  but I wasn't able to find it...]

The documentation for git-log -S includes:

"Look for differences that introduce or remove an instance of <string>.
 Note that this is different than the string simply appearing in diff output"

But I want to do that "different" thing (IOW I want search the diff output).

So must I loop through git-rev-list, grepping git-diff output on each commit?

Or if it _is_ possible to search the diff output directly then it
might be useful
to link to the relevant description instead of saying what -S doesn't do.

Thanks - Eric