I haven't seen "on crack" used in a positive light, but apparently it is sometimes? Usually I'd say "they must have a crack team on incident response", meaning a highly functional, smooth-running team.
For example, it would not be out of the question to say something like “when the iPhone launched it was amazing. Like a palm pilot on crack.”
So, when used positively, “on crack” is generally a modifier(in my experience). When used alone it does seem to have negative connotations.
In this context though, OP is referring to the drug where the Github engineers are being quick/energetic about fixing the issue because they're "boosted" by the drug's effects.
I'm more used to 'on crack' meaning like 'delirious, over confident'.