Syntax highlighting is terrible and has been for 6 years.
Finish shamrock.
Figure out how to compile it as a standalone program. Think it just depends on oniguruma.
Figure out how to test it. Collect as many examples of each language as possible and then run both old and new SH, output as plain text then diff to make sure there's no deviations.
Finally figure out how to plumb shamrock into Chocolat, including changing CHScope into a wrapper around shamrock::Scope and CHLineMarker into a wrapper around shamrock::LineMarker.
Syntax highlighting is terrible and has been for 6 years.