feat: using `tfenv pin` to pin the current tf version to `.terraform-version`

[nitrocode]

when I run this

tfenv install latest:^0.14
tfenv use latest:^0.14
terraform version

I'm using the latest terraform version but I'd also like to pin down this version to a file using a command like this

• tfenv pin or perhaps
• tfenv pin > .terraform-version

At the moment, I use this in an alias

alias tfenv-pin="tfenv list | grep '^*' | cut -d' ' -f2 > .terraform-version && cat .terraform-version"