title: For Emacs, how to bind keys only in certain action?
body: <p>Specifically, I'd like to change the key bindings of Emacs-Helm.  When I run <code>helm-find-files</code>, if I hit <code>C-z</code> on a directory, you can jump into the selected directory.  I'd like to change this behavior to <code>Tab</code>.  I know the action bound to <code>C-z</code> is <code>helm-execute-persistanet-action</code>.  I can achieve this by doing <code>(global-set-key (kbd "&lt;tab&gt;") 'helm-execute-persistanet-action)</code> but then that will capture all other <code>tab</code> actions.  I only want <code>tab</code> to run <code>helm-execute-persistanet-action</code> when I'm in <code>helm-find-files</code></p>