line wrapping

[mookid]

On a diff with very long lines, diffr helps but reading unified diff is still hard.

Implement a flag that wraps long lines before highlighting differences. This is almost as running diff -u file1 file2 | fold | diffr instead of diff -u file1 file2 | diffr, except that the fold command is aware of leading "+/-" characters.

see https://blog.robertelder.org/terminal-diff-tool/ that tries to do something clever.