diffstat: scale adds/removes proportionally to graph width
The previous method of scaling had a tendency to include graph lines that
went past the output width when the file with the most changes had a very
large number of changes.
patch: create file even if source is not /dev/null
as long as the first hunk is -0,0 and the source and destination have the
same name. Matt found a patch like this, and /usr/bin/patch accepts it.