This fixes https://savannah.gnu.org/bugs/?49750.

Achieve this by reusing the code that gives feedback when trying to
save a buffer while using --tempfile and the file has no name yet.

This fixes https://savannah.gnu.org/bugs/?48622.

Achieve this elegantly by factoring out the reading of one rcfile.

Kind-of-discovered-by: Markus Bergholz <markuman@gmail.com>

Also when somehow key_defined() is missing.

This fixes https://savannah.gnu.org/bugs/?49614

.
Reported-by: Mike Frysinger <vapier@gentoo.org>

(Bug was introduced yesterday, by commit a4132e2e.)

This fixes the two bugs reported by Anton Minaev
in https://savannah.gnu.org/bugs/?49511.

This fixes https://savannah.gnu.org/bugs/?49530.

When giving a line number on the command line, do_gotolinecolumn() needs
to know the width of the screen to be able to (roughly) place the target
line in the center of the screen.

This fixes https://savannah.gnu.org/bugs/?49462.

The nanorc option already exists, but not the corresponding one
for the command line.

This fixes https://savannah.gnu.org/bugs/?49428.

It does not update anything -- it just picks a new point from
where to start displaying the buffer.  All actual updating of
the screen is done by edit_refresh() and edit_redraw() and such.

This fixes https://savannah.gnu.org/bugs/?49406.

There is no need to look at this for every painted line, because
the margin can only change when some key is struck.

Instead of doing this in two places: after interpreting shortcuts,
and after injecting characters.

It can be activated with --linenumbers on the command line or with
'set linenumbers' in a nanorc file, and it can be toggled with M-#.
Signed-off-by: Faissal Bensefia <faissaloo@gmail.com>
Signed-off-by: Benno Schulenberg <bensberg@justemail.net>

This fixes https://savannah.gnu.org/bugs/?49099,
and fixes the unreported corresponding bugs for
<End> and <Del> and typing extra characters.

And also case-sensitive searches, backward searches, and searching again.

Mentioning "GNU nano" instead of "This program" and referring to the
website instead of to a postal address.

Resetting the cutbuffer is irrelevant when 'allow_funcs' is false or
when in view mode, so do_input() can just return in those cases.

Add the keycodes and routines to allow the user to forego setting the
mark explicitly (with M-A / ^6) and instead quickly select a few words
or lines by holding down Shift together with the movement keys.

(Some combinations with Shift are swallowed by some terminal emulators.
To work around some of those, the combinations Shift+Alt+Left/Right work
as Shift+Home/End and Shift+Alt+Up/Down work as Shift+PageUp/PageDown.)

This fixes https://savannah.gnu.org/bugs/?48787.

That is: don't try to look at open files when none are open yet.

This fixes https://savannah.gnu.org/bugs/?48520.

This fixes https://savannah.gnu.org/bugs/?48751 reported by Andrew Ho.

This also fixes compilation when configured with --enable-tiny.

If this breaks your build, please send report or instructions or patch.

Straightforward code is more important than the tiniest possible binary.

Also adjust some comments and rename a variable.