working with many many remotes, e.g. emacs starter kit, dotfiles, gitx forks, etc

ignore_local_remote_branches.sh

# delete (locally) remote branches older than 2013 ("not" 2013)
git branch -r | while read i; do git log -n 1 $i --pretty=format:"%ci" | grep -e '^2013' && echo $i || git branch -r -d $i; done 

# delete (locally) remote branches which are fully merged into another remote branch
git branch -r | grep -v origin/HEAD | while read branch; do git branch -r --merged $branch | grep -v $branch; done | sort | uniq | while read rm_branch; do git branch -r -d $rm_branch; done

# Remove (locally) all branches on all remotes which are merged into their own $origin/master. Set that remote to only sync those branches.
git remote | while read i; do git ls-remote -h $i | sed "s,.*refs/heads/,$i/,"; done > all_heads;
git remote | while read i; do git branch -r --merged $i/master | grep $i | grep -v master; done > up_to_date_with_master;
git remote | while read i; do grep $i all_heads > branch_heads; grep $i up_to_date_with_master >> branch_heads; sort branch_heads | uniq -u | sed "s,$i/,," > branch_heads_keep; uniq -d branch_heads_keep | while read j; do  git branch -r -d $i/$j; done; cat branch_heads_keep | xargs git remote set-branches $i; git remote prune $i; done