Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Introduce centralized [X]dialog(1) exit codes to `dialog.subr' and make-use
throughout the bsdconfig(8) code. While we're here, add an explicit argument
to lvalue-seeking invocations of "return" that previously had no argument.
Also, consolidate a single instance of double-newline and remove some
comments that are no longer required (given increased readability with new
exit codes).

Approved by: re (glebius)

Use f_show_msg() instead of f_dialog_msgbox() where appropriate. The main
difference between these two functions:

Usage: f_show_msg() $format_string [ $format_args ... ]
Usage: f_dialog_msgbox() $text [ $hline ]

The former lends itself well to displaying the $msg_* i18n text, prompts,
etc. While the latter is better for text you do not control (error strings
captured as a response from external commands) -- or if you have to control
the hline.

Standardize the way functions build their arguments leading up to a dialog
invocation. Specifically, "top-load" your arguments and in the order in-
which they will be displayed. For example, many [if not all] widgets display
information in the following order, top-to-bottom (visually):

+ backtitle (displayed behind the widget at top-left)
+ title (at the top of the `window')
+ prompt text (just below the title and above whatever widget you choose)
+ Depending on widget, _one_ of the following:
- menu list
- radio list
- check list
- text input box with initial text
- [Xdialog(1)] 2x or 3x text input boxes
- [dialog(1)] a multi-part form
- progress bar
- etc. (many more widget choices)
+ buttons (right below the selected widget)
+ [dialog(1)] the hline (displayed at bottom of `window')

NOTE: Xdialog(1) accepts and silently ignores --hline

When building local arguments for your dialog invocation, if the value can't
be cleanly loaded into a local, add "# Calculated below" to the end of the
local declaration while retaining the block order of argument declarations.

Move other local declarations that are not associated with this top-loading
the dialog arguments to right-above where they are first-used.

Also, standardize on the names of the arguments. For example, always use
$prompt (instead of sometimes $msg and sometimes $prompt); use $menu_list
or $shell_list or $radio_list for those respective widgets; ad nauseum.

While we're doing this, flush-out full arguments for many invocations that
were passing NULL strings (making it unapparent if you were staring at this
one invocation what argument that NULL string was supposed to represent).

Last, while we're in startup/rcconf let's remove the unnecessary use of a
GLOBAL (RCCONF_MENU_LIST) for the menu_list.

Similar to r251236, improve the portion of dialog(1) API in dialog.subr
responsible for retrieving stored input (for the --inputbox and --password
widgets).

When we (Ron McDowell and I) developed the first version of bsdconfig, it
used temporary files to store responses from dialog(1). That hasn't been
true for a very long time, so the need to always execute some clean-up
function is long-deprecated. The function that used to perform these clean-
up routines for these widgets was f_dialog_inputstr().

We really don't need f_dialog_inputstr() for its originally designed purpose
as all dialog invocations no longer require temporary files.

Just as in r251236, redesign f_dialog_inputstr() in the following four ways:

1. Rename f_dialog_inputstr() to f_dialog_inputstr_fetch()
2. Introduce the new first-argument of $var_to_set to reduce forking
3. Create a corresponding f_dialog_inputstr_store() to abstract storage
4. Offload the sanitization to a new function, f_dialog_line_sanitize()

It should be noted that f_dialog_line_sanitize() -- unlike its cousin from
SVN r251236, f_dialog_data_sanitize() -- trims leading/trailing whitespace
from the user's input. This helps prevent errors and common mistakes caused
by the fact that the new cdialog implementation allows the right-arrow
cursor key to go beyond the last byte of realtime input (adding whitespace
at the end of the typed value).

While we're centralizing the sanitization, let's rewrite f_dialog_input()
while we're here to likewise reduce forking. The f_dialog_input() function
now expects the first argument of $var_to_set instead of producing results
on standard-out.

These changes greatly improve readability and also improve performance.

Improve portion of the dialog(1) API in dialog.subr responsible for
calculating widget sizes. Instead of forking a sub-shell to calculate the
optimum size for a widget, use a byRef style call-out to set variables in
the parent namespace. For example, instead of:

size=$( f_dialog_buttonbox_size title btitle msg )
$DIALOG --title title --backtitle btitle --msgbox msg $size

The new API replaces the above with the following:

f_dialog_buttonbox_size height width title btitle msg
$DIALOG --title title --backtitle btitle --msgbox msg $height $width

This reduces the number of forks, improves performance, and makes the code
more readable by revealing the argument-order for widget sizing. It also
makes performing minor adjustments to the calculated values easier as
you no longer have to split-out the response (which required knowledge of
ordering so was counter-intuitive).

UI improvements. First, implement --default-item whenever and wherever
possible to save keystrokes. Second, overhaul startup/rcdelete for much
improved performance. Last, but not least, kill-off useage of --clear
and implement --keep-tite in harmony to minimize jarring transitions.
Also, fix local variable names where necessary while we're here with
other minor comment-enhancements/typo-corrections.

Don't use f_show_msg() unless printf(1) syntax is required (this reduces the
number of unnecessary forks).

Add more debugging to help with diagnosis of program-flow when needed.

Change all invocations of dialog(1) to no-longer require temporary files.
This allows bsdconfig to -- like bsdinstall -- operate from read-only media.

Reviewed by: adrian (co-mentor)
Approved by: adrian (co-mentor)

Move major includes into /usr/share/bsdconfig for easy external access.

Reviewed by: adrian (co-mentor)
Approved by: adrian (co-mentor)