mattermost: update to version 5.30.3

This should be compatible with the version we currently use, and also include all hot-fixes
etc. which we definitely want to have.

pkgs/default.nix

@@ -34,6 +34,8 @@ let
       '';
     });
 
+    mattermost = callPackage ./mattermost {};
+
     inherit (unstable) bottom;
   };
 

pkgs/mattermost/default.nix

@@ -0,0 +1,58 @@
+{ stdenv, fetchurl, fetchFromGitHub, buildGoPackage, buildEnv }:
+
+let
+  version = "5.30.3";
+
+  mattermost-server = buildGoPackage rec {
+    pname = "mattermost-server";
+    inherit version;
+
+    src = fetchFromGitHub {
+      owner = "mattermost";
+      repo = "mattermost-server";
+      rev = "v${version}";
+      sha256 = "sha256-cqP2gHv3v49EsAp0xVteKeSRSknchclmUV+9d8WN/18=";
+    };
+
+    goPackagePath = "github.com/mattermost/mattermost-server";
+
+    buildFlagsArray = ''
+      -ldflags=
+        -X ${goPackagePath}/model.BuildNumber=nixpkgs-${version}
+    '';
+
+  };
+
+  mattermost-webapp = stdenv.mkDerivation {
+    pname = "mattermost-webapp";
+    inherit version;
+
+    src = fetchurl {
+      url = "https://releases.mattermost.com/${version}/mattermost-${version}-linux-amd64.tar.gz";
+      sha256 = "sha256-ZQKwHZZtyhJEPk05eGZlHSNiQTc/LD+2+4zjfvE278A=";
+    };
+
+    installPhase = ''
+      mkdir -p $out
+      tar --strip 1 --directory $out -xf $src \
+        mattermost/client \
+        mattermost/i18n \
+        mattermost/fonts \
+        mattermost/templates \
+        mattermost/config
+    '';
+  };
+
+in
+  buildEnv {
+    name = "mattermost-${version}";
+    paths = [ mattermost-server mattermost-webapp ];
+
+    meta = with stdenv.lib; {
+      description = "Open-source, self-hosted Slack-alternative";
+      homepage = "https://www.mattermost.org";
+      license = with licenses; [ agpl3 asl20 ];
+      maintainers = with maintainers; [ fpletz ryantm ];
+      platforms = platforms.unix;
+    };
+  }