When you define an alias like alias g=git, the shell will pick it up and run the corresponding autocomplete function. Now, there's a program out there called hub, which is basically a supserset of git, with some added, github-specific functionality. The recommended way to use hub is to alias git=hub. Of course, this won't trigger the autocomplete function for git, which makes sense.
Now, if I wanted to have git's autocomplete trigger for hub, the only way I know of is editing /usr/share/zsh/functions/Completion/Unix/_git and adding hub in the first line as trigger. While this works, it isn't practical, since this file will get overwritten with the next zsh release. Assuming hub won't provide a zsh completion function any time soon, is there another way of adding hub to the trigger commands for git's autocomplete function?