Bash/Git - show local branches and how far ahead/behind they are from remote/origin

branches.sh

#!/usr/bin/env bash
#  show local branches and how far ahead/behind they are from remote/origin

git fetch origin

for branch in $(git branch --format='%(refname:short)'); do
    remote_branch="origin/$branch"
    if git show-ref --verify --quiet refs/remotes/$remote_branch; then
        ahead=$(git rev-list --count $remote_branch..$branch)
        behind=$(git rev-list --count $branch..$remote_branch)
        echo "$branch -> $remote_branch : ahead $ahead, behind $behind"
    else
        echo "$branch -> $remote_branch : does not exist on remote"
    fi
done