remove all branches deleted on remote code example

Example: remove all branches deleted on remote

# set this alias in git.config
git config --global alias.gone "! git fetch -p && git for-each-ref --format '%(refname:short) %(upstream:track)' | awk '\$2 == \"[gone]\" {print \$1}' | xargs -r git branch -D"
# then run
git gone