Add status buildinfo

[faho]

This can be used to get some information on how fish was built - the version, the build system, the operating system and architecture, the features.

The idea is that we can tell people to run status buildinfo | fish_clipboard_copy and copy it into bug reports.

Example output:

> ./fish -c 'status buildinfo'
Build system: CMake
Version: 3.7.1-2571-gaadcb292b
Target (and host): x86_64-unknown-linux-gnu
Profile: release
Features: gettext

> ../target/x86_64-unknown-linux-musl/debug/fish -c 'status buildinfo'
Build system: Cargo
Version: 3.7.1-2571-g79aee4d60
Target: x86_64-unknown-linux-musl
Host: x86_64-unknown-linux-gnu
Profile: debug
Features: installable

This seems like it might be useful especially since we have multiple build systems and the potential for cross-compilation now.

The exact set of things to print isn't set in stone, of course, this was just what I came up with.

An alternative is to make a status debuginfo command that is a bit broader in scope, and also prints e.g. terminal or locale information, possibly even the operating system.

Importantly, this should not collect information like the time it was compiled to not break build reproducability, nor should it (for obvious reasons) collect personal information.

TODOs:

• Changes to fish usage are reflected in user documentation/manpages.
• Tests have been added for regressions fixed
• User-visible changes noted in CHANGELOG.rst

[mqudsi]

fyi I previously added separate status modes target and target-arch as part of #10582 but as they were incidental to the fix rather than an intentional feature (though I found them valuable in all cases) @ridiculousfish was of the opinion that they should be removed.

+1 from me :)

[faho]

@ridiculousfish was of the opinion that they should be removed.

I'm aware, I understood the issue to be that you added an undocumented command to provide this information for use in one insignificant test.

I want to have it as a proper thing. Documented and meant to be used.

The impetus here is that I'm expecting some amount of confusion about whether to build with cargo or cmake. And so I would at least want to have an easy way to figure that out.

[mqudsi]

Suggestion: I would add at least crt-static to the features list, possibly pcre2-static as well.

[faho]

Suggestion: I would add at least crt-static to the features list, possibly pcre2-static as well.

crt-static: Sure, why not

pcre2-static: I don't know how to do that. It's not a feature of the fish crate, it's one of the pcre2-sys crate that's decided when that is compiled. I also don't think it's going to help because I don't think it's a source of problems.

[faho]

Okay, I'd like to get this one in for 4.0, because it'll be useful in case someone e.g. manages to accidentally build as self-installable.

[faho]

Cherry-picked to 4.0 as 5f76fc3