This diff-highlight is much slower than the perl version that is bundled with git

[martin-t]

I ran into this issue when diffing 1fc57d61e3a699b4fca9b4ad026ee34b2267bcd5 and 25eebc377c1c59b260354c75f659cfb9f8fceefd in this repo. It's not a typical diff but it shouldn't just hang forever.

The per script is in /usr/share/doc/git/contrib/diff-highlight/diff-highlight