E.g. if we do `string match -q`, and we find a match, nothing about
the input can change anything, so we quit early.
This is mainly useful for performance, but it also allows `string`
with `-q` to be used with infinite input (e.g. `yes`).
Alternative to #7495.
Instead of informing the bell character (hex 07), the example was using
an escaped \ followed by x07.
$ echo \\x07
\x07
$ echo \x07
$ echo \x07 | od -a
0000000 bel nl
0000002
$
* docs: Use \u instead of \\u
Instead of informing the Unicode character 慡, this example was using an
escaped \ followed by u6161.
$ echo \\u6161
\u6161
$ echo \u6161
慡
Before:
$ string escape --style=var 'a1 b2'\\u6161 | string unescape --style=var
a1 b2\u6161
Now:
$ string escape --style=var 'a1 b2'\u6161 | string unescape --style=var
a1 b2慡