git-nym

#!/bin/bash

# NYM=... - part of *unique* key name of any ~/.ssh/id_*
# NYM_CLEAN=flag - if set, uses "clean" ssh - without control/agent sockets

# XXX: with git-2.3, also possible with GIT_SSH_COMMAND var

[[ -n "$NYM_RUN" ]] && {
	extras=
	[[ -n "$NYM_CLEAN" ]] && {
		extras=( -o ControlPath=none -o ControlMaster=no )
		export SSH_AGENT_PID= SSH_AUTH_SOCK=
	}
	exec ssh "${extras[@]}" -o PasswordAuthentication=no -i "$NYM" "$@"
}
[[ -z "$NYM" ]] && { echo >&2 "No NYM env var set"; exit 1; }

[[ ! -e "${NYM}" ]] && {
	p="${HOME}/.ssh/${NYM}"
	[[ -e "$p" ]] && export NYM_RUN=true NYM=$p
	[[ -z "${NYM_RUN}" ]] && {
		for t in rsa ecdsa ed25519; do
			p="${HOME}/.ssh/id_${t}__${NYM}"
			[[ ! -e "$p" ]] && continue
			export NYM_RUN=true NYM=$p
			break
		done
	}
	[[ -z "${NYM_RUN}" ]] && {
		readarray -t ids < <(ls -1 "$HOME"/.ssh/id_* | grep -F "$NYM" | grep -v '\.pub$')
		[[ ${#ids[@]} -gt 1 ]] && {
			echo >&2 "More than one ID matching NYM ('${NYM}'): ${ids[@]}"
			exit 2; }
		[[ ${#ids[@]} -le 0 ]] && {
			echo >&2 "Failed to find ID matching NYM ('${NYM}'): ${ids[@]}"
			exit 2; }
		export NYM_RUN=true NYM=${ids[0]}
	}
}

GIT_SSH=$0 exec git "$@"