github.com/golang/mock/mockgen now included into callers

[mtrmac]

Hello!

#1802 has added a dependency on github.com/golang/mock/mockgen to the top-level subpackage.

As a result, callers like https://github.com/containers/storage which import none of the three subpackages generated by this software now conceptually include the …/mockgen subpackage as a dependency. Luckily, right now, it is completely optimized out (no functions are called, and there are no inits), but that’s not guaranteed.

I’m not entirely sure what is the impact of importing the package in #1802 ; would it perhaps be possible to move tools.go to a separate subpackage, tools/tools.go, so that callers of this library don’t directly depend on the code of the generator tools?

[helsaawy]

@mtrmac
Can you check if #1840 solves this issue?

[mtrmac]

Thanks! Looks great.