Fredrik Kuivinen [off-list ref] writes:
There is another possible optimisation with respect to xdiff. Instead
of producing the diff on the xdiff side and parsing the diff in
blame.c, we could add another call back which just gets the relevant
information from the hunk header. I don't know how much we would gain
from this, but it might be worth a try.
I've tried and then it turned out it did not make much of a
difference.