>
> If the user option 'completion-auto-select' is set to t, then pressing 
> tab should pop up the completions buffer and select the first option. 
> This works well, unless a file name is being completed.  In that case, 
> tab doesn't jump to completion buffer.  In fact it appears not to even 
> open it by default.  A second press opens the buffer, but only jumps if 
> you don't do anything else for about half a second.  A third press of 
> the tab key jumps to the second option.  So if you press tab three 
> times, without waiting, you always skip the first completion suggestion.
>
> The issue can be reproduced with emacs -Q, by evaluating (setq 
> completion-auto-select t) and then opening a file using C-x C-f, in 
> presumably any directory.
>

Thanks for your bug report.  If I set completion-auto-select in emacs -Q, 
C-x C-f C TAB (or TAB TAB, depending on the value of 
completion-auto-select) in the Emacs repository behaves as expected. 
However, C-x C-f src/ TAB does not.  Is the latter case what you have in 
mind, or do I misunderstand what you mean?  If not, the attached patch 
should fix that bug.