glide {get,install,update} breaks vendor submodule

[dt]

In our vendor workflow, we opted to make vendor a submodule, so we'd get the benefits of checking in deps (e.g. maintaining distribution, reproducibility, etc) without adding the actual content of dep changes to our main repo history (our vendor is ~200mb right now).

However, glide replaces the vendor directory with a newly built one after every operation, which has the side effect of deleting the vendor/.git submodule pointer.

Our current workaround is to just move .git aside and replace it after.

[sdboyer]

We've had a few issues raised about the underlying issue here (recreating the vendor dir in its entirety, every time). Handling this particular case might not actually be that bad, though. Lemme see...