docs/cli: new page

README.md

@@ -14,7 +14,7 @@ To manually specify upstream servers:
 
     go run ./cmd/koushin imaps://mail.example.org:993 smtps://mail.example.org:465
 
-See `-h` for more information.
+See `docs/cli.md` for more information.
 
 ## Themes
 

docs/cli.md

@@ -0,0 +1,42 @@
+# SYNOPSIS
+
+    koushin [options...] <upstream servers...>
+
+# DESCRIPTION
+
+koushin is a simple and extensible webmail. It offers a web interface for IMAP,
+SMTP and other upstream servers.
+
+At least one upstream IMAP server needs to be specified. The easiest way to do
+so is to just specify a domain name:
+
+    koushin example.org
+
+This assumes SRV DNS records are properly set up (see [RFC 6186]).
+
+Alternatively, one or more upstream server URLs can be specified:
+
+    koushin imaps://mail.example.org:993 smtps://mail.example.org:465
+
+The following URL schemes are supported:
+
+* `imaps` (IMAP with TLS), `imap+insecure` (plain IMAP)
+* `smtps` (SMTP with TLS), `smtp+insecure` (plain SMTP)
+* `https` (CardDAV and CalDAV over HTTPS), `http+insecure` (CardDAV and CalDAV
+  over plain HTTP)
+* `carddavs` (CardDAV over HTTPS), `carddav+insecure` (CardDAV over plain HTTP)
+* `caldavs` (CalDAV over HTTPS), `caldav+insecure` (CalDAV over plain HTTP)
+
+# OPTIONS
+
+**-theme**: default theme (default: no theme)
+
+**-addr**: listening address (default: ":1323")
+
+**-h**, **--help**: show help message and exit
+
+# SIGNALS
+
+**SIGUSR1**: reloads templates and Lua plugins
+
+[RFC 6186]: https://tools.ietf.org/html/rfc6186