diffs: drop diffs.differ...
diffs: drop diffs.differ
This function did not really add any value, it was yet another layer that was
hiding the bug that we use ref[1] without ref[0], and it had this strange
undefined behaviour for diffing across repos.
Inlining the call to .get_diff do not make the code more complex but makes it
more obvious what is going on so it can be cleaned up later.
