Utility to handle creating and using GitHub deploy keys

gh-ssh

#!/bin/sh

set -euo pipefail

dir=~/.ssh/github.com

name=$(basename "$0")

help=$(printf "\
usage: %s [-d] [repo]
       %s -l
       %s -D
" "$name" "$name" "$name")

usage() {
	printf "%s\n" "$help" >&2
	exit 2
}

setup() {
	SSH_AUTH_SOCK=$dir/.agent
	export SSH_AUTH_SOCK
	eval "$(ssh-agent -a "$SSH_AUTH_SOCK" 2>/dev/null)"
	# Create a new agent if the connection fails
	if [ "$(ssh-add -l 2>/dev/null 1>&2 || echo $?)" = 2 ]; then
		rm "$SSH_AUTH_SOCK"
		eval "$(ssh-agent -a "$SSH_AUTH_SOCK" 2>/dev/null)"
	fi
}

del=
while getopts :dlD opt; do
	case $opt in
	d) del=1 ;;
	l) setup && ssh-add -l; exit ;;
	D) setup && ssh-add -D; exit ;;
	?) usage
	esac
done
shift $((OPTIND-1))

repo=${1-$(gh repo view --json nameWithOwner -q .nameWithOwner)}
key=$dir/$repo

if [ "$del" ]; then
	setup && ssh-add -d "$key"
	exit
fi

keys=$(gh repo deploy-key -R "$repo" list | cut -f4)

# Generate key if doesn't exist
if ! [ -e "$key" ]; then
	mkdir -p "$(dirname "$key")"
	ssh-keygen -C "git@github.com:$repo.git" -f "$key"
fi

# Add to GitHub if doesn't exist
if ! echo "$keys" | grep -qxF "$(awk '{print $1,$2}' "$key.pub")"; then
	gh repo deploy-key -R "$repo" add "$key.pub"
fi

setup

# Add to agent if doesn't exist
if ! ssh-add -L | grep -qxF "$(cat "$key.pub")"; then
	ssh-add "$key"
fi