diffstat: with --git, mark binary files with Bin
Normally, diffs without any text insertions or deletions are reported
as having 0 lines changed by stock diffstat. Compatibility is
preserved with stock diffstat in this case, but when using --git,
binary files are marked with Bin as a means of clarification.
git diff --stat does something similar, though it also includes the
old and new file sizes.
adding base
foo/renamed
renamed
bar/renamed
renamed
baz
.hg/patches/baz
% test patch being renamed before committed