Previously we would call pullFiles() from the pick() handler if we were not in a
rebase, assuming that the default keybinding for both is "p". This needn't be
the case of course, if the user has remapped one or the other.
The consequence of this was that swapping the keybindings for "pullFiles" and
"pushFiles" would work in all panels except the Commits panel (unless "pick" was
also remapped in the same way).
Fix this by using the new AllowFurtherDispatching mechanism of DisabledReasons
to pass the keybinding on to the next handler.
c752f3529b