feat: Allow for custom global tool-versions location

[brianvanburken]

Summary

Since a recent bug fix to the behaviour around the env variable ADSF_DEFAULT_TOOL_VERSIONS_FILENAME, which I also abused to follow the XDG spec, I was unable to move my global .tool-versions. As was also reported by other people in #1248.

This PR allows the user to give a custom location via ASDF_CONFIG_DIR if set (for those who want it to move the file and don't follow the XDG spec), XDG_CONFIG_HOME, or falls back to HOME.

I'm open to suggestions if another approach is better.

Related issues: #687

[jthegedus]

I only took a quick look, but I think there are some aspects missing from this. Importantly is the resolution of .tool-versions, it is just a walk up the directory tree, where the location of global is not special and simply likely to be part of the users current working directory. Your solution would break this behaviour.

I also think we could utilise Bats test conventions to unset the XDG value in a single place instead of in each individual test.

[jwierzbo]

@brianvanburken instead of using ASDF_CONFIG_DIR, could you provide new ENV - ASDF_GLOBAL_TOOL_VERSIONS_PATH? That would be more handful to use and also all logic could stay in place

[jthegedus]

ASDF_GLOBAL_TOOL_VERSIONS_PATH would still require more work from this PR to actually work though, as current lookup of Global is at $HOME/ADSF_DEFAULT_TOOL_VERSIONS_FILENAME. We would need to change the lookup method.

[brianvanburken]

@jthegedus Thank you for taking the time to look at my PR! I'll improve the testing using your feedback.

I'm not so familiar with the project so bear with me. I looked at the code as how it resolves global and local .tool-versions. As far as I can see, there are two branches; one branch checks directly the location of the global files. The other branch looks locally in the folder and walks upward as you described. My PR targets the global file and allows users to move this using different options. I think walking up the directory tree for the file is irrelevant, if I'm not mistaken. Could you tell me more specifically what aspect I'm missing here?

As for the ASDF_GLOBAL_TOOL_VERSIONS_PATH, it is a small change to make. But, I'm looking at a bit bigger picture. I saw that there is a ASDF_DATA_DIR variable where everything data related is stored for asdf. So in the same spirit, using ASDF_CONFIG_DIR, we could also implement a future change to store .asdfrc in that directory.

I'm currently finishing up some things at work before my vacation, so I'm a bit swamped. When I return, I'll finish the implementation in one week.

[brianvanburken]

I've switched from asdf and won't know about the project and bash, along with time, to finish this. If anyone wants to pick up where I left off, feel free to take my code