_do_a_fancy_diff(): Pay no attention to the ellipses behind the curtain.

_do_a_fancy_diff():  Pay no attention to the ellipses behind the curtain.

While a fancy diff can be confusing in the presence of ellipses, so far
I'm finding (2-0-0) that it's much more a major aid in narrowing down the
possibilities when an ellipsis-slinging test fails.  So we no longer
refuse to do a fancy diff just because of ellipses.

This isn't ideal; it's just better.