When I type git sub<TAB>, the completion works as expected: the fragment is expanded to git submodule. When I type git sub<TAB> up<TAB>, the completion does not work.
git sub<TAB> up<TAB>
I've also noticed that git ls-f<TAB> is also not completed as expected (git ls-files).
Patch coming for missing subcommands.
By default I only provide completion for common git commands, but you can add $GitTabSettings.AllCommands = $true to your profile to enable completion for everything.
$GitTabSettings.AllCommands = $true
Add subcommand expansion for bisect, notes and submodule
Nice one, thanks! I'll give that config setting a go as well if I run into the problem again.