I found it hard going to start up a single instance of the gpg-agent
daemon, as recommended in the man page not to run multiple instances.

It'd be good there was an option like --write-env-file, but writing the
file only if it doesn't already contain a running daemon (info which
reaches a running daemon, that is).  No doubt there'd be some locking in
case there's two such "start if not already running" going on at the
same time.

It'd also be good if such a startup didn't actually communicate with the
running instance, just check its socket isn't an EPIPE or something like
that, so it doesn't slow down your login from .bashrc or whatever.

Better still would be not to actually start a daemon at all until a
program wants to do some signing.  Maybe a "GPG_AGENT_FILE" could set a
place to read/write for a "start if not already running" on-demand.