Current 'git add -p' will say "No changes." if there are no changes to
text files, which can be confusing if there _are_ changes to binary
files. Add some code to distinguish the two cases, and give a
different message in the latter one.
Signed-off-by: Thomas Rast <trast@student.ethz.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>