fix(env): Retro-compatible precedence order for variables with defaults set in Dockerfile

- `BLOCK_NSA` has precedence over `BLOCK_SURVEILLANCE`
- `HEALTH_OPENVPN_DURATION_ADDITION` has precedence over `HEALTH_VPN_DURATION_ADDITION`
- `HEALTH_OPENVPN_DURATION_INITIAL` has precendence over `HEALTH_VPN_DURATION_INITIAL`
- Chain of precedence: `PROXY` > `TINYPROXY` > `HTTPPROXY`
- Chain of precedence: `PROXY_LOG_LEVEL` > `TINYPROXY_LOG` > `HTTPPROXY_LOG`
- `PROTOCOL` has precendence over `OPENVPN_PROTOCOL`
- `IP_STATUS_FILE` has precendence over `PUBLICIP_FILE`
- `SHADOWSOCKS_PORT` has precedence over `SHADOWSOCKS_LISTENING_ADDRESS`
- `SHADOWSOCKS_METHOD` has precedence over `SHADOWSOCKS_CIPHER`

internal/configuration/sources/env/publicip.go

@@ -35,17 +35,17 @@ func readPublicIPPeriod() (period *time.Duration, err error) {
 }
 
 func (r *Reader) readPublicIPFilepath() (filepath *string) {
-	s := os.Getenv("PUBLICIP_FILE")
-	if s != "" {
-		return &s
-	}
-
 	// Retro-compatibility
-	s = os.Getenv("IP_STATUS_FILE")
+	s := os.Getenv("IP_STATUS_FILE")
 	if s != "" {
 		r.onRetroActive("IP_STATUS_FILE", "PUBLICIP_FILE")
 		return &s
 	}
 
+	s = os.Getenv("PUBLICIP_FILE")
+	if s != "" {
+		return &s
+	}
+
 	return nil
 }