Make zigup configurable through an enviroment

[Mulling]

This PR adds a few things and ideas:

• Makes zigup configurable through an environment, defined at $ZIGUP_DIR/env. Inline with Support system-wide configuration for zigup directory #113;
• Allows zigup to auto-configure itself (with minimal action required by the user);
• Replaces --install-dir and --path-link with $ZIGUP_INSTALL_DIR and $ZIGUP_DIR. Inline with Proposal: Rename the zig compiler storage directory from zig to .zig or .zig-compilers #148;
• Rework how the default compiler is set (needs testing on Windows), fixes Add a symbolic link to the files of the default compiler #69;
• Allows zigup default to set the default compiler from a path, i.e., zigup default zig/build;
• Adds zigup undefine to unset the current default compiler;
• Reworks logging and adds a flag, -v or --verbose, to enable verbose output;

Overall, this makes zigup work when installed globally (from a package manager); and allows persistent configuration. For now, only tested on Linux.

[marler8997]

See my comments on other issues/PRs for my thoughts on adding support for environment variable configuration.

[Mulling]

Care to explain? You could do away with the environment variables, that's not a problem, it'd still need an environment (like cargo and others). + it would allow for zigup to be packaged, without the problems from it being in the global path that happen now. This also avoids having the user pass --install-dir all the time or creating aliases.

[marler8997]

Previous comment/thoughts here: #91 (comment) (see the linked comment in that comment)

I'm not aware of any problems with packaging zigup at the moment.

[Mulling]

I'm not aware of any problems with packaging zigup at the moment.

Using the AUR package as an example: zigup gets installed under /usr/bin/ and attempts to symlink the downloaded version to /usr/bin/zig. This not only breaks a multi-user system, but also does not allow the user to have zig installed through the package manager. Solution is to use --path-link, which comes back to the problem at hand.

If contributions are welcomed I'm happy to make changes, like removing the environment variables (still need an environment to configure the PATH).

[marler8997]

Ah i see yes that is a problem. I'm thinking the solution here might be to add a build-option so that distribution maintainers can specify the default path-link at build time for their distribution. What do you think? Does arch have a standard directory for the user to place binaries (or in this case a symlink to a binary) meant to be accessible via PATH ?

[Mulling]

Most distros will have ~/.local/bin in the PATH, you could use that. I still think an env file that just adds a path in the zigup install dir to the PATH is a better option (rustup/cargo, ghcup, etc... all use this approach).

[marler8997]

Well I have no problem with adding a build option to change the default path link, something like zig build -Dpath-link=~/.local/bin sounds fine to me. Adding support for environment variables and environment files would be adding complexity that I think would need justification. That's the type of complexity that makes triaging issues a pain as you now need to know alot more about the user's environment to understand whats going on.

[Mulling]

Understandable, I will maintain a fork here: https://github.com/mulling/zup with the changes above and more, if anyone is interested.