Move manifest generation to apps.generate-manifest

This makes it fairly easier to generate manifests in downstream
repositories.

apps/default.nix

@@ -11,6 +11,16 @@ rec {
       program = "${drv}/bin/linux-image";
     };
 
+  generate-manifest = let
+    drv = import ./generate-manifest {
+      stdenv = packages.stdenv;
+      inherit nixpkgs dhallApps;
+    };
+  in {
+    type = "app";
+    program = "${drv}/bin/generate-manifest";
+  };
+
   nova-image = let
     drv = import ./nova-image {
       stdenv = packages.stdenv;

apps/generate-manifest/default.nix

@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: CC0-1.0
+
+{ stdenv, nixpkgs, dhallApps }:
+
+with nixpkgs.buildPackages;
+
+writeScriptBin "generate-manifest" ''
+  #!${runtimeShell}
+  root="$1"
+  if [ -z "$root" ]; then
+    echo a directory must be passed as an argument >> /dev/stderr
+    exit 1
+  fi
+  if [ ! -d "$root" ]; then
+    echo \'$root\' is not an existing directory >> /dev/stderr
+    exit 1
+  fi
+  set -eu
+  find="${findutils}/bin/find"
+    echo -n '{'
+    if [ -d "$root/bin" ]; then
+      echo -n ',bin = {'
+      find $root/bin/ -type f -printf '%f "%p"\n' \
+        | awk '{print ", "gensub(/\..*/, "", 1, $1)"={mapKey= \""$1"\",mapValue ="$2"}"}'
+      echo -n '}'
+    fi
+    if [ -d "$root/lib" ]; then
+      echo -n ',lib = {'
+      find $root/lib/ -type f -name '*.lib.so' -printf '%f "%p"\n' \
+        | awk '{print ", "gensub(/\..*/, "", 1, $1)"={mapKey=\""$1"\",mapValue="$2"}"}'
+      echo -n '}'
+    fi
+    if [ -d "$root/tar" ]; then
+      echo -n ',tar = {'
+      find $root/tar/ -type f -name '*.tar' -printf '%f "%p"\n' \
+        | awk '{print ""gensub(/\..*/, "", 1, $1)"={mapKey=\""$1"\",mapValue="$2"}" }'
+      echo -n '}'
+    fi
+    echo '}'
+''

flake.nix

@@ -30,7 +30,7 @@
           packages = import ./packages {
             inherit system legacyPackages;
             depot = thisSystem genode-depot.packages;
-            dhallApps = dhall-haskell.apps.${localSystem};
+            apps = self.apps.${localSystem};
           };
 
           defaultPackage = packages.genode.base-linux;

packages/default.nix

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: CC0-1.0
 
-{ system, legacyPackages, depot, dhallApps }:
+{ system, legacyPackages, depot, apps }:
 
 let
   inherit (legacyPackages) callPackage;
@@ -10,30 +10,7 @@ let
   mkDhallManifest = drv:
     legacyPackages.runCommand "${drv.name}.dhall" {
       inherit drv;
-      dhall = dhallApps.dhall.program;
-    } ''
-      echo '{' >> manifest.tmp
-      if [ -d $drv/bin ]; then
-        echo ', bin = {' >> manifest.tmp
-        find $drv/bin/ -type f -printf '%f "%p"\n' \
-          | awk '{print ", "gensub(/\..*/, "", 1, $1)" = { mapKey = \""$1"\", mapValue = "$2" }" }'>> manifest.tmp
-        echo '}' >> manifest.tmp
-      fi
-      if [ -d $drv/lib ]; then
-        echo ', lib = {' >> manifest.tmp
-        find $drv/lib/ -type f -name '*.lib.so' -printf '%f "%p"\n' \
-          | awk '{print ", "gensub(/\..*/, "", 1, $1)" = { mapKey = \""$1"\", mapValue = "$2" }" }'>> manifest.tmp
-        echo '}' >> manifest.tmp
-      fi
-      if [ -d $drv/tar ]; then
-        echo ', tar = {' >> manifest.tmp
-        find $drv/tar/ -type f -name '*.tar' -printf '%f "%p"\n' \
-          | awk '{print ""gensub(/\..*/, "", 1, $1)" = { mapKey = \""$1"\", mapValue = "$2" }" }'>> manifest.tmp
-        echo '}' >> manifest.tmp
-      fi
-      echo '}' >> manifest.tmp
-      $dhall < manifest.tmp > $out
-    '';
+    } "${apps.generate-manifest.program} $drv > $out";
 
   addManifest = drv: { manifest = mkDhallManifest drv; } // drv;