Panic on underflow

[casey]

I think that there are scenarios where this subtraction can underflow and panic:

if let Some(Difference::Rem(removed)) = diffs.get(i - 1) {

The line is here:

colored-diff/src/lib.rs

Line 75 in 42ba173

if let Some(Difference::Rem(removed)) = diffs.get(i - 1) {

I'm sorry for not providing a good reproduction case, I got a crash but couldn't stop to come up with a minimal reproduction

[CAD97]

If the text starts with an Add then the subtraction will underflow, thus panicking in debug mode. It will work properly in release mode. I can't patch this for a bit (I'm super busy rn), but the simple fix is just to wrapping subtract. If you send me a PR to fix it I'll pull it and push a new version sooner than I'd get to it otherwise.

[CAD97]

Fixed by #4 and released as v0.2.2! 🎉