Some refinements

app/src/main/java/com/topjohnwu/magisk/receivers/DownloadReceiver.java

@@ -52,5 +52,5 @@ public abstract class DownloadReceiver extends BroadcastReceiver {
         mFilename = filename;
     }
 
-    public void task(Uri uri) {}
+    public abstract void task(Uri uri);
 }

app/src/main/java/com/topjohnwu/magisk/receivers/RepoDlReceiver.java

@@ -0,0 +1,43 @@
+package com.topjohnwu.magisk.receivers;
+
+import android.net.Uri;
+
+import com.topjohnwu.magisk.R;
+import com.topjohnwu.magisk.utils.Async;
+import com.topjohnwu.magisk.utils.Utils;
+import com.topjohnwu.magisk.utils.Utils.ByteArrayInOutStream;
+import com.topjohnwu.magisk.utils.ZipUtils;
+
+import java.io.OutputStream;
+
+public class RepoDlReceiver extends DownloadReceiver {
+    @Override
+    public void task(Uri uri) {
+        // Flash the zip
+        new Async.FlashZIP(mContext, uri, mFilename){
+            @Override
+            protected void preProcessing() throws Throwable {
+                // Process and sign the zip
+                publishProgress(mContext.getString(R.string.zip_install_process_zip_msg));
+                ByteArrayInOutStream buffer = new ByteArrayInOutStream();
+
+                // First remove top folder (the folder with the repo name) in Github source zip
+                ZipUtils.removeTopFolder(mContext.getContentResolver().openInputStream(mUri), buffer);
+
+                // Then sign the zip for the first time
+                ZipUtils.signZip(mContext, buffer.getInputStream(), buffer, false);
+
+                // Adjust the zip to prevent unzip issues
+                ZipUtils.adjustZip(buffer);
+
+                // Finally, sign the whole zip file again
+                ZipUtils.signZip(mContext, buffer.getInputStream(), buffer, true);
+
+                // Write it back to the downloaded zip
+                OutputStream out = mContext.getContentResolver().openOutputStream(mUri);
+                buffer.writeTo(out);
+                out.close();
+            }
+        }.exec();
+    }
+}