add meta attributes to all images

augment the images with meta attributes from the input packages.

and then use the meta.description as dockerhub metadata.

nix/default.nix

@@ -10,44 +10,47 @@
 , nix
 , xz
 }:
-dockerTools.buildImageWithNixDb {
-  inherit (nix) name;
+let
+  image = dockerTools.buildImageWithNixDb {
+    inherit (nix) name;
 
-  contents = [
-    ./root
-    coreutils
-    # add /bin/sh
-    bash
-    nix
+    contents = [
+      ./root
+      coreutils
+      # add /bin/sh
+      bash
+      nix
 
-    # runtime dependencies of nix
-    cacert
-    gitMinimal
-    gnutar
-    gzip
-    xz
+      # runtime dependencies of nix
+      cacert
+      gitMinimal
+      gnutar
+      gzip
+      xz
 
-    # for haskell binaries
-    iana-etc
-  ];
-
-  extraCommands = ''
-    # for /usr/bin/env
-    mkdir usr
-    ln -s ../bin usr/bin
-
-    # make sure /tmp exists
-    mkdir -m 0777 tmp
-  '';
-
-  config = {
-    Cmd = [ "/bin/bash" ];
-    Env = [
-      "ENV=/etc/profile.d/nix.sh"
-      "NIX_PATH=nixpkgs=channel:nixpkgs-unstable"
-      "PAGER=cat"
-      "PATH=/usr/bin:/bin"
-      "SSL_CERT_FILE=${cacert}/etc/ssl/certs/ca-bundle.crt"
+      # for haskell binaries
+      iana-etc
     ];
+
+    extraCommands = ''
+      # for /usr/bin/env
+      mkdir usr
+      ln -s ../bin usr/bin
+
+      # make sure /tmp exists
+      mkdir -m 0777 tmp
+    '';
+
+    config = {
+      Cmd = [ "/bin/bash" ];
+      Env = [
+        "ENV=/etc/profile.d/nix.sh"
+        "NIX_PATH=nixpkgs=channel:nixpkgs-unstable"
+        "PAGER=cat"
+        "PATH=/usr/bin:/bin"
+        "SSL_CERT_FILE=${cacert}/etc/ssl/certs/ca-bundle.crt"
+      ];
+    };
   };
-}
+in
+  image // { meta = nix.meta // image.meta; }