Use less_than_a_screenful() again, just as in do_uncut_text().

Most of these variables are freed moments later -- reallocating
them is thus a waste of time.

Windows doesn't have *nix style account databases.

With read_file() revamped, it now uses partition_filestruct() indirectly
via ingraft_buffer(), so we can't use partition_filestruct() to replace
marked text in the alternate spell checker anymore without segfaulting.

Add the new function replace_marked_buffer() to accomplish this instead.
Based on replace_buffer(), it uses extract_buffer() to throw away the
marked un-spell-checked text, and then uses read_file() to insert the
spell-checked text at the position where the mark was.

Accordingly, remove unneeded partitioning and related stuff from
do_alt_speller().  Besides pasting the file into the buffer at
current[current_x], ingraft_buffer() also deals with renumbering,
updating totsize, and handling a magicline, so do_alt_speller()
doesn't need to do those anymore.

With read_file() revamped to handle inserting a file at the current
position, partitioning the buffer is no longer needed.

Move buffer handling and '\r' stripping from read_line() to read_file(),
so that the file gets its format determined and gets stored in its own
buffer entirely in one function.  Then use ingraft_buffer() to insert
this new buffer into the current one.

In addition to pasting the file at current[current_x], ingraft_buffer()
also deals with renumbering, the updating of totsize, and the handling
of a magicline, so read_file() doesn't need to do those anymore.

Note that all this makes read_file() depend on the position of
current[current_x] to know where to insert the file.  Accordingly,
set current_x to zero in initialize_buffer_text() instead of in
make_new_buffer(), so that replace_buffer() keeps working properly.

This fixes https://savannah.gnu.org/bugs/?49892.

This fixes https://savannah.gnu.org/bugs/?49994

.
Reported-by: David Lawrence Ramsey <pooka109@gmail.com>

Instead of setting openfile->current_y (and wrongly so), just call
reset_cursor() to recompute current_y and place the cursor on that
line (if it is not offscreen).

The conditionalizing saved negligible amounts of space, of memory, and
of speed.

This makes nano's cursor behavior consistent across 1) typing text by
hand; 2) pasting in text with ^U; 3) inserting text from a file; and
4) redoing with M-E that same typing or pasting or inserting.

This fixes https://savannah.gnu.org/bugs/?49968.

The warning is wrong when the user has just saved a buffer under a
new name.  And when --quickblank is used, the warning most likely
gets cleared off before it is seen, and the user would just hear
the beep and be left wondering what happened.

This avoids https://savannah.gnu.org/bugs/?49875.

When a given file is, for example, unreadable or unwritable, the
error message should use ^J instead of ^@ in its name.

In path names and file names, 0x0A means an embedded newline and
should be shown as ^J, but in anything related to the file's data,
0x0A is an encoded NUL and should be displayed as ^@.

So... switch mode at the two main entry points into the "file system"
(reading in a file, and writing out a file), and also when drawing the
titlebar.  Switch back to the default mode in the main loop.

This fixes https://savannah.gnu.org/bugs/?49893.

Decode 0x0A bytes to 0x00 when saving the search history, and encode
them again when reading the file back in, to prevent nano from hanging
or aborting when encountering 0x00 on a line by itself.

After updating the color palette, the corresponding new window content
should be drawn immediately, before some other part of the code calls
doupdate(), to prevent the old content being shown in the new colors.

This fixes https://savannah.gnu.org/bugs/?49912

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

This fixes https://savannah.gnu.org/bugs/?49884.

Taking the terminating newline into account, and that there is
at least one digit per number.

A filename might contain spaces, so we can't look for the numbers
(the second and third elements) starting from the head of the line
-- we have to start at the tail and work backward.

This fixes https://savannah.gnu.org/bugs/?49879.

(I don't /see/ single-letter variables -- they are too small.)

It is irrelevant -- the line is discarded as soon as the data has been
extracted.

So they will not break a line in the positionlog file in two.

(Strangely, the reading in of such a log file already decodes
nulls back into newlines.)

This fixes https://savannah.gnu.org/bugs/?49877.

Because changing anything to a null effectively means to truncate
the name.

This fixes https://savannah.gnu.org/bugs/?49868
and fixes https://savannah.gnu.org/bugs/?49874.

Most full paths are needed only temporarily and will be freed within
milliseconds.  Only 'full_operating_dir' and 'backup_dir' continue to
exist for the whole current session.  Any partition, too, will soon be
unpartitioned, so the extra reallocation is just a waste of time.

It doesn't align anything -- any allocations are already aligned to
whatever multiple is required -- it just shrinks the allocated space.

And which normally is just some ten or twenty characters long, and
never gets wildly overallocated.