bin/159775: handling of autoboot_delay="-1" has changed in 9.0

[Colin Percival]

>Number:         159775
>Category:       bin
>Synopsis:       handling of autoboot_delay="-1" has changed in 9.0
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Aug 15 01:10:08 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Colin Percival
>Release:        9.0-BETA1
>Organization:
>Environment:
FreeBSD 9.0-BETA1
>Description:
The handling of autoboot_delay="-1" has changed with the new boot loader scripts.  

In /boot/defaults/loader.conf, the old behaviour is documented:
#autoboot_delay="10"            # Delay in seconds before autobooting,
                                # set to -1 if you don't want user to be
                                # allowed to interrupt autoboot process and
                                # escape to the loader prompt, set to
                                # "NO" to disable autobooting

In the menu.4th man page, the new behaviour is documented:
           autoboot_delay
                     Number of seconds menu-display will wait before executing
                     menu_timeout_command (boot by default) unless a key is
                     pressed.  If set to ``NO'' (case-insensitive) or ``-1'',
                     menu-display will wait for user input and never execute
                     menu_timeout_command.  Default is ``10''.  See loader(8)
                     for additional information.

Note that "user can't interrupt boot process" and "menu-display will never execute menu_timeout_command" are nearly exact opposite behaviours.
>How-To-Repeat:
Set autoboot_delay="-1" on 9.0-BETA1.  Be astonished by what happens.
>Fix:
Either change menu.4th to restore the old behaviour, or update the comments in /boot/defaults/loader.conf (and possibly add an entry to the release notes to warn users).

>Release-Note:
>Audit-Trail:
>Unformatted: