eclipse.plugins: unpack plugins when required

Some plugin bundles must be unpacked when used in Eclipse. With this
change the plugin manifest is checked for the setting indicating that
unpacking should happen.

pkgs/applications/editors/eclipse/plugins.nix

@@ -49,16 +49,35 @@ rec {
       installPhase = ''
         dropinDir="$out/eclipse/dropins/${name}"
 
+        # Install features.
         cd features
         for feature in *.jar; do
-          feat=''${feature%.jar}
-          mkdir -p $dropinDir/features/$feat
-          unzip $feature -d $dropinDir/features/$feat
+          featureName=''${feature%.jar}
+          mkdir -p $dropinDir/features/$featureName
+          unzip $feature -d $dropinDir/features/$featureName
         done
         cd ..
 
+        # Install plugins.
         mkdir -p $dropinDir/plugins
-        cp -v "plugins/"*.jar $dropinDir/plugins/
+
+        # A bundle should be unpacked if the manifest matches this
+        # pattern.
+        unpackPat="Eclipse-BundleShape:\\s*dir"
+
+        cd plugins
+        for plugin in *.jar ; do
+          pluginName=''${plugin%.jar}
+          manifest=$(unzip -p $plugin META-INF/MANIFEST.MF)
+
+          if [[ $manifest =~ $unpackPat ]] ; then
+            mkdir $dropinDir/plugins/$pluginName
+            unzip $plugin -d $dropinDir/plugins/$pluginName
+          else
+            cp -v $plugin $dropinDir/plugins/
+          fi
+        done
+        cd ..
       '';
     });