The default value of GIT_SERVER is "github.com" even if GIT_KIND isn't "github"

[monaka]

Referring to the description in README.md,

GIT_SERVER : the URL of the server if not using the public hosted git providers:

So the default value of GIT_SERVER should be https://gitlab.com if they set gitlab as GIT_KIND.
But it looks that the default value of GIT_SERVER is always https://github.com.

It can be avoided by setting GIT_SERVER='https://gitlab.com' explicitly.