Temporary you can remove them running `git branch -r --merged | grep -v -e "\(origin\|your\-github\-name\)/" | xargs -n 1 git branch -r -d`
Temporary you can remove them running
git branch -r --merged | grep -v -e "\(origin\|your\-github\-name\)/" | xargs -n 1 git branch -r -d