prometheus-mysqld-exporter: add meta.changelog

pkgs/servers/monitoring/prometheus/mysqld-exporter.nix

@@ -11,8 +11,8 @@ buildGoModule rec {
   src = fetchFromGitHub {
     owner = "prometheus";
     repo = "mysqld_exporter";
-    rev = "v${version}";
-    sha256 = "sha256-uHr9hVjnQx1DIr7ByaqgmR4YOvCYo49+b+Ikh+Vlh+o=";
+    tag = "v${version}";
+    hash = "sha256-uHr9hVjnQx1DIr7ByaqgmR4YOvCYo49+b+Ikh+Vlh+o=";
   };
 
   vendorHash = "sha256-fM3CqyOEKYJOFkEwBE7/yIQEKUUIbBIbmHQp12/psas=";
@@ -37,6 +37,7 @@ buildGoModule rec {
   ];
 
   meta = with lib; {
+    changelog = "https://github.com/prometheus/mysqld_exporter/blob/${src.tag}/CHANGELOG.md";
     description = "Prometheus exporter for MySQL server metrics";
     mainProgram = "mysqld_exporter";
     homepage = "https://github.com/prometheus/mysqld_exporter";