in German translation of QtCreator, open a git project, edit a file, press Alt+G,C to commit something.
Now you get a dialog where you can enter the description.

You see a button named &Abgeben (commit), there is a checkbox with the title "&Alle markieren" (mark all), and if you press Alt+A, neither of the both happen, but you open the Application menu "&Analsye" which seems to have priority.