Documentation for /usr/lib/dovecot/imap executable

Dear Dovecot experts,

I'm in the process of setting up dovecot with mbsync as a local cache for remote IMAP servers. One recipe that I found involves using the /usr/lib/dovecot/imap (This is with Debian's dovecot package). For example, in .mbsyncrc I have

IMAPAccount cwg-wf-local RequireSSL no Tunnel "/usr/lib/dovecot/imap -o mail_location=maildir:/home/cwg/.mail/cwg-wf"

This works, but I wonder: is there any documentation for the /usr/lib/dovecot/imap executable? What options does it take? If there's no documentation: where can I find this command in dovecot's sources?

Thank you, Christoph