config: add message-store memory

The old way to do this was `message-store fs ""`, which is
misleading.

cmd/soju/main.go

@@ -86,7 +86,7 @@ func loadConfig() (*config.Server, *soju.Config, error) {
 	cfg := &soju.Config{
 		Hostname:        raw.Hostname,
 		Title:           raw.Title,
-		LogPath:         raw.LogPath,
+		LogPath:         raw.MsgStoreSource,
 		HTTPOrigins:     raw.HTTPOrigins,
 		AcceptProxyIPs:  raw.AcceptProxyIPs,
 		MaxUserNetworks: raw.MaxUserNetworks,

config/config.go

@@ -45,7 +45,9 @@ type Server struct {
 
 	SQLDriver string
 	SQLSource string
-	LogPath   string
+
+	MsgStoreDriver string
+	MsgStoreSource string
 
 	HTTPOrigins    []string
 	AcceptProxyIPs IPSet
@@ -64,6 +66,7 @@ func Defaults() *Server {
 		Hostname:        hostname,
 		SQLDriver:       "sqlite3",
 		SQLSource:       "soju.db",
+		MsgStoreDriver:  "memory",
 		MaxUserNetworks: -1,
 		MultiUpstream:   true,
 	}
@@ -110,12 +113,18 @@ func parse(cfg scfg.Block) (*Server, error) {
 				return nil, err
 			}
 		case "message-store", "log":
-			var driver string
+			if err := d.ParseParams(&srv.MsgStoreDriver); err != nil {
-			if err := d.ParseParams(&driver, &srv.LogPath); err != nil {
 				return nil, err
 			}
-			if driver != "fs" {
+			switch srv.MsgStoreDriver {
-				return nil, fmt.Errorf("directive %q: unknown driver %q", d.Name, driver)
+			case "memory":
+				srv.MsgStoreSource = ""
+			case "fs":
+				if err := d.ParseParams(nil, &srv.MsgStoreSource); err != nil {
+					return nil, err
+				}
+			default:
+				return nil, fmt.Errorf("directive %q: unknown driver %q", d.Name, srv.MsgStoreDriver)
 			}
 		case "http-origin":
 			srv.HTTPOrigins = d.Params

doc/soju.1.scd

@@ -133,9 +133,15 @@ The following directives are supported:
 	  strings, see:
 	  <https://pkg.go.dev/github.com/lib/pq#hdr-Connection_String_Parameters>.
 
-*message-store* fs <path>
+*message-store* <driver> [source]
-	Path to the bouncer logs root directory, or empty to disable logging. By
+	Set the database location for IRC messages. By default, an in-memory message
-	default, logging is disabled.
+	database is used.
+
+	Supported drivers:
+
+	- _memory_ stores messages in memory.
+	- _fs_ stores messages on disk, in the same format as ZNC. _source_ is
+	  required and is the root directory path for the database.
 
 	(_log_ is a deprecated alias for this directive.)