git remote remove origin fatal no such remote 'origin'

The above will only work if you've either cloned the repository or manually added a remote called origin.

If "git remote -v" doesn't show you any remotes you can simply add a remote using:

git remote add origin https://username@stash/scm/PROJECT/repo.git
The name of the remote doesn't have to be "origin" and can be any name that makes it easier for you to identify that particular remote (e.g. "stash").

HTH,

Stefangit remote set-url origin https://github.com/your/repository