We can't always read in chunks because we often can't bear to
overread:
```fish
echo foo\nbar | begin
read -l foo
read -l bar
end
```
needs to have the first read read `foo` and the second read `bar`. So
here we can only read one byte at a time.
However, when we are directly redirected:
```fish
echo foo | read foo
```
we can, because the data is only for us anyway. The stream will be
closed after, so anything not read just goes away. Nobody else is
there to read.
This dramatically speeds up `read` of long lines through a pipe. How
much depends on the length of the line.
With lines of 5000 characters it's about 15x, with lines of 50
characters about 2x, lines of 5 characters about 1.07x.
See #8542.
Changes it from
```
$fish_color_user: not set in local scope
$fish_color_user: set in global scope, unexported, with 1 elements
$fish_color_user[1]: length=3 value=|080|
$fish_color_user: set in universal scope, unexported, with 1 elements
$fish_color_user[1]: length=7 value=|brgreen|
```
(with the trailing empty line - not just a newline)
to
```
$fish_color_user: set in global scope, unexported, with 1 elements
$fish_color_user[1]: |080|
$fish_color_user: set in universal scope, unexported, with 1 elements
$fish_color_user[1]: |brgreen|
```
It's now good enough to do so.
We don't allow grid-alignment:
```fish
complete -c foo -s b -l barnanana -a '(something)'
complete -c foo -s z -a '(something)'
```
becomes
```fish
complete -c foo -s b -l barnanana -a '(something)'
complete -c foo -s z -a '(something)'
```
It's just more trouble than it is worth.
The one part I'd change:
We align and/or'd parts of an if-condition with the in-block code:
```fish
if true
and false
dosomething
end
```
becomes
```fish
if true
and false
dosomething
end
```
but it's not used terribly much and if we ever fix it we can just
reindent.
Do this only when splitting on IFS characters which usually contains
whitespace characters --- read --delimiter is unchanged; it still
consumes no more than one delimiter per variable. This seems better,
because it allows arbitrary delimiters in the last field.
Fixes#6406
This splits a string into variables according to the shell's
tokenization rules, considering quoting, escaping etc.
This runs an automatic `unescape` on the string so it's presented like
it would be passed to the command. E.g.
printf '%s\n' a\ b
returns the tokens
printf
%s\n
a b
It might be useful to add another mode "--tokenize-raw" that doesn't
do that, but this seems to be the more useful of the two.
Fixes#3823.