This is great, thank you!
Can you add a test for this, or modify one of the existing tests?

I just added aliases to the existing AutoComplete tests, and updated the expected outputs. The only thing that I'm not sure about is why in AutoCompleteTest#testComplete() I need to repeat each alias three times. Any idea?

The only thing that I'm not sure about is why in AutoCompleteTest#testComplete() I need to repeat each alias three times. Any idea?

I will have to take a look in the debugger to see what is going on. It may take some time before I can get to this.

I finally had some time to take a look at this.
It appears that the AutoComplete#filterAndTrimMatchingPrefix method does not filter out duplicates, even though it should. This can be fixed by modifying the first line of this method to use a Set instead of a List:

    private static void filterAndTrimMatchingPrefix(String prefix, List<CharSequence> candidates) {
        Set<CharSequence> replace = new HashSet<CharSequence>();
        ...

The expectations in testComplete can then be changed to also have only one occurrence of each of the subcommand aliases, which makes much more sense.

Can you change the PR accordingly?

PR has been updated with all requested changes

Merged.
Thank you for the contribution!

I will update the release notes when I get to my PC.