The output looks somewhat similar to color-words diffs. Unified diffs are
verbose, but are easier to follow if adjacent lines are added/removed + modified
for example.
Word-level diffing is forcibly enabled. We can also add a config knob (or
!color condition) to turn it off to save CPU time.
I originally considered disabling highlights in block insertion/deletion, but
that wasn't always great. This can be addressed separately as it also applies
to color-words diffs. #3958
44a39017f0