I suspect Apple's document on this subject is incorrect. In the section titled "Monitoring the progress of installing software updates" it shows:
I saw no such indicator today. I now see from Apple's doc, that I could have looked at Launchpad, but that is incidental.
I will now chronicle the scenario that happened to me today so others can see how important this is.
- I got a notification that updates were ready to install but some could not be updated automatically.
- I clicked Install.
- A dialog box appeared telling me to shut down Xcode.
- I shut down Xcode.
- I waited a few minutes.
- I opened App Store and clicked Updates.
- I noticed Acorn 4 (an image editing app) had been updated today.
- I saw no other indication that updates were occurring.
- I wondered why Acorn 4 would require me to shut down Xcode. It never had before. Usually only Apple system updates require that.
- I started Xcode and began to work again. Some time passed.
- I tabbed back to the App Store app.
- I noticed that iTunes had finished updating.
- I then recalled that iTunes is one of the apps which require me to shut down Xcode during an update.
To me, this situation is very dangerous. What if my starting up of Xcode during that iTunes update had corrupted my Xcode or iTunes installation? Actually, at this time, I am not certain that it did not.