local branches

List local branches which have been merged in master

git branch --merged master

Remove these local merged branches, make sure you are on master and updated to newest

git checkout master && git pull origin master

git branch --merged master | egrep -v "(^\*|master)" | xargs git branch -d

remote branches

List remote branches which have been merged in master

git branch -r --merged master

Remove these remote branches, make sure you are on master and updated to newest

git checkout master && git pull origin master

git branch -r --merged master | egrep -v "(^\*|master)" | sed 's_ *origin/__' | xargs -I% git push origin --delete %