Wrapper around `ssh` to pick the right one from several GitHub deploy keys

ssh-deploy-key-wrapper.sh

#!/bin/bash

# The last argument is the command to be executed on the remote end, which is something
# like "git-upload-pack 'webfactory/ssh-agent.git'". We need the repo path only, so we
# loop over this last argument to get the last part of if.
for last in ${!#}; do :; done

# Don't use "exec" to run "ssh" below; then the trap won't work.
key_file=$(mktemp -u)
trap "rm -f $key_file" EXIT

eval last=$last

# Try to pick the right key
ssh-add -L | grep --word-regexp --max-count=1 $last > $key_file

ssh -i $key_file "$@"

This wrapper script can be used when you need to use more than a single deploy key for GitHub.com. Keys can be kept in the ssh-agent, and the right key will identified through a key comment.

See https://www.webfactory.de/blog/using-multiple-ssh-deploy-keys-with-github.

Note to self: We could add this script somewhere to https://github.com/webfactory/ssh-agent.

Actions will be checked out in the worker, but we'd need to expand $HOME/work/_actions/webfactory/ssh-agent/*/....

Thank you very much for this wrapper script. However, for now, I can work without it. Once I created my deploy keys (one per repository) and added each key to its respective github repository (the the repository's settings), and loaded these keys in the ssh agent, I found that github.com will allow me to clone any of my repositories with the first deploy key the agent offers it. Regardless whether that particular key belongs to that repository or any of my other ones. I think that this is a bug and I posted a question in the GitHub community forums about it.