allow use of assets server without any provider

README.md

@@ -88,6 +88,8 @@ By default no request log generated. This can be turned on by setting `--logger.
 
 User may turn assets server on (off by default) to serve static files. As long as `--assets.location` set it will treat every non-proxied request under `assets.root` as a request for static files. 
 
+Assets server can be used without any proxy providers. In this mode reproxy acts as a simple web server for a static context.
+
 ## More options
 
 - `--gzip` enables gizp compression for responses.

app/main.go

@@ -164,7 +164,7 @@ func makeProviders() ([]discovery.Provider, error) {
 		res = append(res, &provider.Static{Rules: opts.Static.Rules})
 	}
 
-	if len(res) == 0 {
+	if len(res) == 0 && opts.Assets.Location == "" {
 		return nil, errors.Errorf("no providers enabled")
 	}
 	return res, nil

examples/file/Makefile

@@ -5,6 +5,11 @@ run: install
 	../../dist/reproxy --file.enabled --file.name=reproxy.yml --assets.location=./web --assets.root=/static
 	pkill -9 whoami
 
+run_assets_only: install
+	../../dist/reproxy --assets.location=./web --assets.root=/
+
+	pkill -9 whoami
+
 kill:
 	pkill -9 whoami