using additional test flags disables caching

[aybabtme]

I noticed that https://github.com/rsc/gt/blob/master/main.go#L499-L500 makes is so that flags such as -cover or -race disable the use of the cache. I'm assuming this is on purpose, I'm curious to know why? Our CI script run our tests with those flags and they are the part that would benefit most from caching.

Also, sorry if I'm pestering you with my questions =].

[rsc]

It's done because in general (1) even parsing the flags is non-trivial, and (2) the flags may affect the validity and reproducibility of the run.

It would be easy to allow -race, which I've now done.

Allowing -cover would require simulating the -cover behavior, namely caching not just the test result but also the coverage output and rewriting the coverage output when replaying a cached result. It's not obvious how far down that road we want to go. If we do coverage, what about cpu profiles or memory profiles?