Jakub Narebski [off-list ref] writes:
So the question is how to color combined diff format (what should be syntax
highlighting for combined diff format). If branches columns have only
pluses we use the same color as for adding line in ordinary diff; if
branches column consist only of minuses we use the same color as for
removing line in ordinary diff. Can there be mixture of plusses and
minuses? How git-diff --color solves this?
UTSL ;-).
Otherwise (iow, if you refuse to use the source), you could
cheat and let "git diff" do the coloring for you, and then
regexp replace the output. You could even use the same coloring
logic for normal diff if you did so.