In NixOS, the best way for us to provide a public-inbox module would be
to generate the configuration file ahead of time, and then initialize
inboxes that don't already exist at some reasonable time during boot.

public-inbox-init tries to write a config file in addition to
initializing an inbox.  My initial idea was to just eschew
public-inbox-init for doing git init --bare myself, which works great
for V1 repositories, but I'd really like to be generating V2 ones.

Since the V2 initialization isn't encapsulated in one easy command, I'm
wondering what the best way to accomplish initialization without writing
a config file or asking for unnecessary information is.  I could just
run public-inbox-init with PI_CONFIG=/dev/null, but then it's still not
clear to me what information about the mailbox the script requires to be
able to initialize the mailbox.  Looking at the code, I see that at
least the primary address is passed to PublicInbox::Inbox, but I'm not
sure what that would actually be used for inside the inbox.

So, what would the best thing for me to do here be?  To summarise, I'd
like to generate V2 inboxes while providing as little information about
the inbox as possible, and without writing a config file.