Empty environment of the spawned git process

[darth]

The modification of the environment of spawned process in 8377e9b actually replaces the environment that is normally inherited from the parent process with the one that contains only GIT_TERMINAL_PROMPT=0. Such a replacement can be source of different problems. For example, in my case spawned git process is not aware that it must use proxy (environment variables HTTP_PROXY/HTTPS_PROXY) to clone repos.
As far as I understand it is sort of "limitation" of underlying libuv uv_spawn function, there is no way to extend the parent process environment, only inherit or replace it.
Possible fix is to temporarily modify vim.env.GIT_TERMINAL_PROMPT before spawning a process and then to reset it back to the original value. Although it feels too much dirty for me.

[savq]

@darth Paq now makes a copy of the current environment so that doesn't happen. should be ok now.