A bunch of our variables are only relevant for interactive use, but
this is two whole sections on them. Simply move them inside "Syntax
highlighting" and leave the link in Special Variables.
* Try to set LC_CTYPE to something UTF-8 capable
When fish is started with LC_CTYPE=C (even just effectively, often via
LC_ALL=C!), it's basically broken. There's no way to handle non-ASCII
characters with a C locale unless we want to write our
locale-independent replacements for all of the system functions.
Since we're not going to do that, let's try to find *some locale* for
LC_CTYPE.
We already do that in __fish_setlocale, but that's
- a bit of a weird thing that reads unstandardized system
configuration files
- allows setting locale to C explicitly
So it's still easily possible to end up in a broken configuration.
Now, the issue with this is that there is (AFAICT) no portable way to
get a list of all allowed locales and C.UTF-8 is not standardized, so
we have no one locale to fall back on and are forced to try a few. The
list we have here is quite arbitrary, but it's a start.
Python does something similar and only tries C.UTF-8, C.utf8 and
"UTF-8".
Once C.UTF-8 is (hopefully) standardized, that will just start
working (tm).
Note that we do not *export* the fixed LC_CTYPE variable, so external
programs still have to deal with the C locale, but we have no real
business messing with the user's environment.
To turn it off: $fish_allow_singlebyte_locale, if set to something true (like "1"),
will re-run the locale initialization and skip the bit where we force
LC_CTYPE to be utf8-capable.
This is mainly used in our tests, but might also be useful if people
are trying to do something weird.
The file is called "config.fish", not "init.fish". We'll call it
"configuration" now.
"Initialization" might be slightly more precise, but in an irritating
way.
Also some wording improvements to the section. In particular we now
mention config.fish *early*, before the whole shebang.
It's not super clear what $SHLVL is useful for, but the current
definition is essentially
"number of shells in the parent processes + 1"
which isn't *super useful*?
Bash's behavior here is a bit weird in that it increments $SHLVL
basically always, but since it auto-execs the last process it will
decrement it again, so in practice it's often not incremented.
E.g.
```
> echo $SHLVL
1
> bash -c 'echo $SHLVL; bash'
2
>> echo $SHLVL
2
```
Both bashes here end up having the same $SHLVL because this is
equivalent to `echo $SHLVL; exec bash`. Running `echo $SHLVL` and then
`bash -c 'echo $SHLVL'` in an interactive bash will have a different
result (1 and 2) because that doesn't *exec* the inner bash.
That's not something we want to get into, so what we do is increment
$SHLVL in every interactive fish. Non-interactive fish will simply
import the existing value.
That means if you had e.g. a bash that runs a fish script that ends up
opening a new fish session, you would have a $SHLVL of *2* - one for the
bash, and one for the inner fish.
We key this off is_interactive_session() (which can also be enabled
via `fish -i`) because it's easy and because `fish -i` is asking for
fish to be, in some form, "interactive".
That means most of the time $SHLVL will be "how many shells am I deep,
how often do I have to `exit`", except for when you specifically asked
for a fish to be "interactive". If that's a problem, we can rethink it.
Fixes#7864.
This breaks apart the massive "index" document into
1. An "index" document that explains how to install and set up fish
and links to the other documents
2. A "fish-language" document that describes the syntax and semantics
of the language
3. A "fish-interactive" document that describes how to use fish
interactively
No change to the content has been made, only the parts have been moved
from index and some of the formatting (links and header levels) were
fixed.
See #7348.
