adga: Add test for all packages

doc/languages-frameworks/agda.section.md

@@ -235,6 +235,13 @@ In a pull request updating e.g. the standard library, you should write the follo
 This will build all reverse dependencies of the standard library,
 for example `agdaPackages.agda-categories`, or `agdaPackages.generic`.
 
+In some cases it is useful to build _all_ Agda packages.
+This can be done with the following Github comment:
+
+```
+@ofborg build agda.passthru.tests.allPackages
+```
+
 Sometimes, the builds of the reverse dependencies fail because they have not yet been updated and released.
 You should drop the maintainers a quick issue notifying them of the breakage,
 citing the build error (which you can get from the ofborg logs).

pkgs/top-level/agda-packages.nix

@@ -13,7 +13,10 @@ let
 
     lib = lib.extend (final: prev: import ../build-support/agda/lib.nix { lib = prev; });
 
-    agda = withPackages [] // { inherit withPackages; };
+    agda = withPackages [] // {
+      inherit withPackages;
+      passthru.tests.allPackages = withPackages (lib.filter (pkg: self.lib.isUnbrokenAgdaPackage pkg) (lib.attrValues self));
+    };
 
     standard-library = callPackage ../development/libraries/agda/standard-library {
       inherit (pkgs.haskellPackages) ghcWithPackages;