Open Radar

 
Summary:
App group container directories are used to share files between apps and between app extensions. Files stored here are not shown in Storage Usage and the user has no way to know how space is being used and by which apps.

Steps to Reproduce:
1. Install Working Copy from https://itunes.apple.com/us/app/working-copy/id896694807?mt=8&ign-mpt=uo%3D6

2. Open the following URL representing a large repository in Safari:
  http://workingcopyapp.com/git/#repo=https://github.com/emacs-mirror/emacs.git 

3. Scroll to the top and tap Open to open the Universal Link in Working Copy.

4. Tap Clone in the upper right corner and sit back and wait for cloning. This repository transfers about 1 gigabytes when cloning.

5. Open the Settings app.

6. Go to General > Storage & iCloud Usage > Manage Storage

Expected Results:
I would expect some entry to show that about 1.3 gigabytes is in use by Working Copy or something associated with Working Copy.

Actual Results:
Working Copy shows a minimal data usage. About 50 megabytes for the app itself and almost nothing for Documents & Data.

The repository was cloned to a App group container directory and only some metadata is stored in the actual Documents directory for Working Copy.

Notes:
I realise there are situations where files in App group containers cannot really be assigned to any one application, so there is difficulty determining which app to "blame".

But there will be some association between apps using the same App group container and picking either one is better than not showing anything. 

In many other situations the App group containers are only used by one main app and its app extensions and picking the main app will be very reasonable.