Best practice to include vendor gem

Hello guys!

I need to include a private gem to a Rails project. I’ve seen some ways to do it by using keys to access private repos, but it seemed excessive for what I needed. The gem won’t be updated so often and, when it does, I will be updating it, so I can re-vendor it.

The problem is: when I added the gem to vendor folder, bundler will raise the message

fatal: Not a git repository (or any of the parent directories): .git

once and a while during deploy.

It seems to be related with the fact that there is a .gemspec file inside its directory. Do you guys ever been throught this? How can I deal with that? Using the private repo solution would be better the vendoring?