Pipe and -conf flag together are an error (#315)

caddy/caddy.go

@@ -282,15 +282,7 @@ func LoadCaddyfile(loader func() (Input, error)) (cdyfile Input, err error) {
 		cdyfile = loadedGob.Caddyfile
 	}
 
-	// Otherwise, we first try to get from stdin pipe
-	if cdyfile == nil {
-		cdyfile, err = CaddyfileFromPipe(os.Stdin)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	// No piped input, so try the user's loader instead
+	// Try user's loader
 	if cdyfile == nil && loader != nil {
 		cdyfile, err = loader()
 	}

main.go

@@ -117,6 +117,19 @@ func mustLogFatal(args ...interface{}) {
 }
 
 func loadCaddyfile() (caddy.Input, error) {
+	// First try stdin pipe
+	cdyfile, err := caddy.CaddyfileFromPipe(os.Stdin)
+	if err != nil {
+		return nil, err
+	}
+	if cdyfile != nil {
+		// it is an error if -conf is also specified because, which to use?
+		if conf != "" {
+			return nil, errors.New("load: can't choose between stdin pipe and -conf flag")
+		}
+		return cdyfile, err
+	}
+
 	// -conf flag
 	if conf != "" {
 		contents, err := ioutil.ReadFile(conf)