Clean Up Old Remote Tracking References
After working on a Git-versioned project for a while, you may find that there are a bunch of references to remote branches in your local repository. You know those branches definitely don't exist on the remote server and you've removed the local branches, but you still have references to them lying around. You can reconcile this discrepancy with one command:
$ git fetch origin --prune
This will prune all those non-existent remote tracking references which is
sure to clean up your git log (git log --graph).