Allow filtering to a specific type of asset task.

build.js

@@ -41,10 +41,20 @@ const fs = require('fs');
         ],
     };
 
-    const files = await assproc.process(env, tasks);
+    const infoPath = process.env.ASSET_INFO_PATH ?? pathJoin(__dirname, 'assets/current.json');
+    let files = {};
 
-    fs.writeFileSync(
-        pathJoin(__dirname, 'assets/current.json'),
-        JSON.stringify(files),
-    );
+    if(process.argv.length > 2) {
+        files = JSON.parse(fs.readFileSync(infoPath));
+
+        const filter = process.argv.slice(2);
+        for(const name in tasks)
+            if(!filter.includes(name))
+                delete tasks[name];
+    }
+
+    fs.writeFileSync(infoPath, JSON.stringify({
+        ...files,
+        ...await assproc.process(env, tasks),
+    }));
 })();