lib/appearance: export $CLICOLOR instead of $LSCOLOR

[gaelicWizard]

Description

• Export $CLICOLOR, instead of $LSCOLORS, and add a comment to the base theme to help theme authors;
• shellcheck;
• Alsö, since the value of $CLICOLOR is not used anywhere, overload it to count the number of colors available for use elsewhere.

Motivation and Context

Exporting $LSCOLOR from lib/appearance has always been weird to me and it took me a few rounds to figure out why: it's not useful. BSD ls enables color output if $CLICOLOR is set (to any value, even blank), and GNU ls doesn't use any variable to enable color listings. (GNU ls requires --color=auto or similar.) The $LSCOLORS (BSD) and $LS_COLORS (GNU) variables do not enable color listings; they just specify which color scheme to use (with incompatible formats).

Themes can and should customize $LSCOLORS/$LS_COLORS, but this should not be hard-coded by the main files. Both GNU and BSD ls have default colors they use when these variables are not set.

Alsö resolves #2082.

How Has This Been Tested?

This is part of my main branch, and I've tested to make sure it loads, and the test suite passes.

Types of changes

• Weird fix (non-breaking change which calms the brain worms)

Checklist:

• My code follows the code style of this project.
• If my change requires a change to the documentation, I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• I have added tests to cover my changes, and all the new and existing tests pass.

[tsiflimagas]

Something related to the code touched here is that LSCOLORS is used by the BSD ls, while the GNU one uses LS_COLORS, which also uses a different format to define colours. I guess that should be set too. The dircolors command outputs a basic set of colours to use, and its output could even be used with eval (well, I guess we'd prefer to just include the variable). What do you think?

[gaelicWizard]

Something related to the code touched here is that LSCOLORS is used by the BSD ls, while the GNU one uses LS_COLORS, which also uses a different format to define colours. I guess that should be set too. The dircolors command outputs a basic set of colours to use, and its output could even be used with eval (well, I guess we'd prefer to just include the variable). What do you think?

Yes, that all sounds like we should address. I would have to spin up a Linux to play with GNU ls. I feel like maybe a plugin/ls is in order 😆

[gaelicWizard]

I found that theme/clean had a generic setting for $LS_COLORS (and a duplicate for $LSCOLORS), so I moved that here now too.

[gaelicWizard]

I made plugin/ls 😃

[NoahGorny]

This is a slightly breaking change, as users will have to enable the plugin so things will work as expected. I am okay with it though

[gaelicWizard]

I'm sorry, I've wrapped around again and I don't think this should be it's own plugin anymore. I think this should be in lib/theme. It's really not a plugin, but actually theme-dependent color scheme (at least for GNU ls). I'll update this PR this weekend.

[gaelicWizard]

Ok guys, totally re-did this branch. Can you check it out again?

[NoahGorny]

Is this ready @gaelicWizard ?
I am okay with merging it

[gaelicWizard]

👍