Clean old and useless remote git branches (Tested with Git v2.21.0 on macOS 10.14 and Git v2.7.4 on Ubuntu 16.04)

git_branch_cleaner.sh

#!/usr/bin/env bash

# The number of branchs you want to keep
KEEP=100

git fetch --all --prune -q

all_remote_branchs_num=$(git branch -r | wc -l | awk '{print $1}')
to_delete_remote_branchs_num=$(($all_remote_branchs_num - $KEEP))
to_delete_remote_branchs=$(git for-each-ref --sort=committerdate --format="%(refname:short)" 'refs/remotes' | head -n $to_delete_remote_branchs_num )

echo ''
echo "Going to delete $to_delete_remote_branchs_num branchs from $all_remote_branchs_num branchs"
echo 'The first branch to delete is:'
# Some old version git doesn't have --pretty="%S", so I have to use ${branch}
branch=$(echo "$to_delete_remote_branchs" | head -n 1)
git show --no-notes --no-patch --pretty="%Cred%h %Cgreen%aI %C(yellow)${branch} %C(cyan)%an %C(auto)- %s" $branch
echo 'The last branch to delete is:'
branch=$(echo "$to_delete_remote_branchs" | tail -n 1)
git show --no-notes --no-patch --pretty="%Cred%h %Cgreen%aI %C(yellow)${branch} %C(cyan)%an %C(auto)- %s" $branch
read -p "Press ENTER to continue. Press CTRL-C to exit. "

echo ''
for branch in $to_delete_remote_branchs
do
    git show --no-notes --no-patch --pretty="Deleting %Cred%h %Cgreen%aI %C(yellow)${branch} %C(cyan)%an %C(auto)- %s" $branch
    ref=$(echo $branch | cut -d '/' -f '2-') # Remove 'origin/' from $branch
    remote=$(echo $branch | cut -d '/' -f '1')
    # Example: $branch is 'origin/release/login'; $ref is 'release/login'; $remote is 'origin'
    git push $remote --delete $ref -q
done