And reword them too, so that it is clearer what the mechanism is
for determining which syntax to use for a file.

Rename the corresponding rc-file option too, of course.

Color it bright green instead, like valid numeric arguments of
'fill' and 'tabsize'.  Also color the argument of 'formatter'.

And in the bargain improve some mark-up here and there.

And rewrap the feature toggles, so that a title does not start
a sentence.

And refer backward instead of forward.

I like it better that ^X stays in the same position compared to the
main screen: the lower left corner.

This fixes https://savannah.gnu.org/bugs/?51457.

The help lines need to be redrawn one step after a justification
(whether it has been undone or not, to replace "Unjustify" with
"Uncut" again for ^U), and after switching buffers (to update a
possibly changed tag for ^T).

This fixes https://savannah.gnu.org/bugs/?51455.

Make them reflect the split into two functions, the direct use of
tabsize, and the difference in behavior between indent and unindent.

Since all indentation and unindentation is by a tab, or by a tab's
worth of spaces, use tabsize directly.

Also remove one unneeded blank line.

The parameter 'cols', that indicates how many columns to indent or
unindent, is changed to be always positive, so the check for being
negative can go.  And it could never be zero anyway.

This is the first step toward splitting them into two dedicated
functions, instead of letting do_indent() handle both cases.

The precalculation of the multiline regexes no longer looks at the
keyboard every second, and the backup code makes use of futimens()
nowadays.

Well, it will compile even without that include.  :|
I don't know why, since it does use va_list.

When compiling with 'clang', it would say: warning: expression which
evaluates to zero treated as a null pointer constant of type 'char *'.

This fixes https://savannah.gnu.org/bugs/?51427.

In nano, -a is only effective when also -$ is given, so this will
not conflict with Pico since Pico does not know the -$ option.

This should eliminate all cases where the newline is pushed off the edge
of the screen in non-atblanks softwrap mode.  Also, it allows the use of
the last column of the screen in atblanks softwrap mode when a piece of
text does not contain any blanks.

This avoids the unreachable end-of-line reported on the mailing list:
http://lists.gnu.org/archive/html/nano-devel/2017-06/msg00011.html.

And then elide the function entirely as it's called just once.

Extend get_softwrap_breakpoint() to break softwrapped lines on
whitespace when a flag is set.  This flag is controlled by the new
rcfile option "atblanks".  The '>' characters marking two-column
characters at the edge of the screen are disabled when it's on.

If get_softwrap_breakpoint() can't find whitespace in screen range, it
will break the line on the screen edge.  (In this case, a blank can be
on the last column of the screen, but text can't, so that a blank on the
last column doesn't become invisible and possibly break the display.)

This fulfills https://savannah.gnu.org/bugs/index.php?49959

.
Requested-by: Nicholas Boel <axxisd@gmail.com>

spotlight() now displays softwrapped lines chunk by chunk instead of all
at once.  Since softwrapped lines are no longer of constant width, the
latter approach would fail if softwrapping breaks the spotlighted text.

Instead of taking a string, spotlight() now takes the starting and ending
columns of that string.  Also, its handling of softwrapped lines is now
split off into a separate function, spotlight_softwrapped().

Use actual_last_column() to properly adjust the cursor if placewewant
is past the end of a softwrapped chunk.

Add the new function actual_last_column() to accomplish this.

get_chunk_row() and get_chunk_leftedge() now become wrappers around
get_chunk(); the latter is only used directly in place_the_cursor()
when we need to get both the row and the leftedge.  get_chunk() now
uses the proper formula to implement varying chunk width.

Since chunk width now varies, place_the_cursor() sets the x position
relative to the leftedge in a different way that works regardless
of chunk width, update_softwrapped_line() loops until it gets all
softwrap breakpoints instead of calculating the full length in
advance and getting one full row at a time, the chunk iterators
now count leftedges instead of rows, and fix_firstcolumn() does a
full recalculation of the chunk that firstcolumn is on instead of
simply shifting it back.

Also, in update_softwrapped_line(), when a line's softwrap breakpoint
is before the last column of the edit window, a ">" is now added to
the end of it.

The workaround in place_the_cursor() for when two-column characters
straddle the edge of the screen is removed, as it's no longer needed
now that chunks end before such characters.

Furthermore, do_home() and do_end() use xplustabs() instead of
placewewant again when calculating the leftedge, since placewewant
refers to a column that may or may not be available (if it's not,
the cursor will be placed wrongly).  Make get_edge_and_target() use
xplustabs() instead of placewewant for the same reason; this also lets
us simplify get_edge_and_target(), since xplustabs() will never be
greater than strlenpt().  Finally, since do_end() now has to calculate
rightedge as well as rightedge_x, use the former to implement the same
time-saving optimizations as in do_home().

The cursor is not yet adjusted when we try to go directly to a column
past the end of a softwrap breakpoint, and placewewant handling in the
vertical movement code is not yet adjusted for varying chunk lengths,
but fixes for these are forthcoming.

This fixes https://savannah.gnu.org/bugs/?49440.