git-cleanup.sh

#!/bin/bash
# This has to be run from master
git checkout master

# Update our list of remotes
git fetch
# Prune stale local branches already removed from origin
git remote prune origin

# Remove local fully merged branches
git branch --merged master | grep -v 'master$' | grep -v 'releases$' | xargs git branch -d

# Show remote fully merged branches
echo "The following remote branches are fully merged and will be removed:" 
git branch -r --merged master | sed 's/ *origin\///' | grep -v 'master$' | grep -v 'releases$'

read -p "Continue (y/N)? " 
case $REPLY in
   y|Y)
      # Remove remote fully merged branches
      git branch -r --merged master | sed 's/ *origin\///' \
        | grep -v 'master$' | grep -v 'releases$' | xargs -I% git push origin :%
      echo "Done!" 
      echo "Obsolete branches are removed" 
      ;;
   *)
      echo "Abort."
      ;;
esac