git fetch Cgit checkout C/stable-branchgit checkout -b myCopy
Then myCopy is a local (copied) branch of C's stable one.
myCopy
In two lines:git fetch Cgit checkout -b myCopy -t C/stable-branch
git fetch C
git checkout -b myCopy -t C/stable-branch
myCopy is now a local branch of C/stable-branch, and is tracking it, so you can do git push and git pull without a refspec.
git push
git pull