Add support key=value pair for cli config

internal/app/README.md

@@ -0,0 +1,54 @@
+- By default go2rtc will search config file `go2rtc.yaml` in current work directory
+- go2rtc support multiple config files
+- go2rtc support inline config as `YAML`, `JSON` or `key=value` format from command line
+- Every next config will overwrite previous (but only defined params)
+
+```
+go2rtc -config "{log: {format: text}}" -config /config/go2rtc.yaml -config "{rtsp: {listen: ''}}" -config /usr/local/go2rtc/go2rtc.yaml
+```
+
+or simple version
+
+```
+go2rtc -c log.format=text -c /config/go2rtc.yaml -c rtsp.listen='' -c /usr/local/go2rtc/go2rtc.yaml
+```
+
+## Environment variables
+
+Also go2rtc support templates for using environment variables in any part of config:
+
+```yaml
+streams:
+  camera1: rtsp://rtsp:${CAMERA_PASSWORD}@192.168.1.123/av_stream/ch0
+
+  ${LOGS:}  # empty default value
+
+rtsp:
+  username: ${RTSP_USER:admin}   # "admin" if env "RTSP_USER" not set
+  password: ${RTSP_PASS:secret}  # "secret" if env "RTSP_PASS" not set
+```
+
+## Defaults
+
+```yaml
+api:
+  listen: ":1984"
+
+ffmpeg:
+  bin: "ffmpeg"
+
+log:
+  level: "info"
+
+rtsp:
+  listen: ":8554"
+  default_query: "video&audio"
+
+srtp:
+  listen: ":8443"
+
+webrtc:
+  listen: ":8555/tcp"
+  ice_servers:
+    - urls: [ "stun:stun.l.google.com:19302" ]
+```

internal/app/app.go

@@ -79,22 +79,26 @@ func Init() {
 	}
 
 	for _, conf := range confs {
-		if conf[0] != '{' {
+		if len(conf) == 0 {
+			continue
+		}
+		if conf[0] == '{' {
+			// config as raw YAML or JSON
+			configs = append(configs, []byte(conf))
+		} else if data := parseConfString(conf); data != nil {
+			configs = append(configs, data)
+		} else {
 			// config as file
 			if ConfigPath == "" {
 				ConfigPath = conf
 			}
 
-			data, _ := os.ReadFile(conf)
+			if data, _ = os.ReadFile(conf); data == nil {
-			if data == nil {
 				continue
 			}
 
 			data = []byte(shell.ReplaceEnvVars(string(data)))
 			configs = append(configs, data)
-		} else {
-			// config as raw YAML
-			configs = append(configs, []byte(conf))
 		}
 	}
 
@@ -190,3 +194,25 @@ func readRevisionTime() (revision, vcsTime string) {
 	}
 	return
 }
+
+func parseConfString(s string) []byte {
+	i := strings.IndexByte(s, '=')
+	if i < 0 {
+		return nil
+	}
+
+	items := strings.Split(s[:i], ".")
+	if len(items) < 2 {
+		return nil
+	}
+
+	// `log.level=trace` => `{log: {level: trace}}`
+	var pre string
+	var suf = s[i+1:]
+	for _, item := range items {
+		pre += "{" + item + ": "
+		suf += "}"
+	}
+
+	return []byte(pre + suf)
+}