git-remote-branch-exists

#!/bin/sh
set -e

usage () {
    echo "usage: git remote-branch-exists [<remote>] <branch>" >&2
    echo >&2
    echo "Will return with an exit code of 0 or 1." >&2
}

if [ $# -eq 1 ]; then
    remote=origin
    branch=$1
elif [ $# -eq 2 ]; then
    remote=$1
    branch=$2
else
    usage
    exit 2
fi

git show-ref --quiet --verify -- "refs/remotes/$remote/$branch"