tests/test-username-newline.out

diff: add --stat for diffstat output

diff/qdiff --stat invokes patch.diffstat() on the diff output.

When in interactive mode, the output's maximum width is determined by the
terminal's width.

adding a
abort: username 'foo\nbar1' contains a newline

abort: username 'foo\nbar2' contains a newline

transaction abort!
rollback completed
abort: username 'foo\nbar3' contains a newline!