add server-side config comment

diff --git a/.offlineimap/preauthtunnel.sh b/.offlineimap/preauthtunnel.sh
index 09769746e0f8e6f8ff85e8f67944a857d59c513a..778cf0d12017d8c69329dca0391831758c552a41 100755 (executable)
--- a/.offlineimap/preauthtunnel.sh
+++ b/.offlineimap/preauthtunnel.sh
@@ -1,3 +1,15 @@
 #!/bin/sh
 
 exec ssh -F ~/.offlineimap/ssh_config -i ~/.offlineimap/${1}.ssh-seckey ${1}
 #!/bin/sh
 
 exec ssh -F ~/.offlineimap/ssh_config -i ~/.offlineimap/${1}.ssh-seckey ${1}

+
+# this relies on the IMAP command being specified on the server side, i.e. in
+# ~/.ssh/authorized_keys, put a line like the following
+#
+#   command="MAIL=$HOME/.maildir /usr/lib/dovecot/imap 2>/dev/null",no-agent-forwarding,no-X11-forwarding,no-port-forwarding,no-pty ssh-ed25519 AAA…
+#
+# Then, when you invoke this script directly, you should see the IMAP server
+# greet you:
+#
+# % ~/.offlineimap/preauthtunnel.sh madduck-net.imap.madduck.net
+# * PREAUTH [CAPABILITY IMAP4rev1 […]] Logged in as madduck
+