bin/brew: better user config home handling

[etcusrvar]

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Feature: improved HOMEBREW_USER_CONFIG_HOME

HOMEBREW_USER_CONFIG_HOME can now be in a few standard locations

1. ~/.homebrew
2. $XDG_CONFIG_HOME/homebrew (if the variable is set)
3. ~/.config/homebrew
4. ~/Library/Application Support/homebrew

See issue #20251 for more details.
I've been using this on both macOS and Linux, without XDG_CONFIG_HOME explicitly set, and it reads my ~/.config/homebrew/brew.env whenever I run the brew command, which is nice.
If the idea meets with approval, I can add any appropriate tests and documentation.

[MikeMcQuaid]

@etcusrvar Let's talk about your use-case specifically: what are you trying to do that the existing code doesn't let you achieve?

[etcusrvar]

@etcusrvar Let's talk about your use-case specifically: what are you trying to do that the existing code doesn't let you achieve?

Specifically, I'd like to have my user brew.env (not the one located in $HOMEBREW_PREFIX/etc/homebrew) located under ~/.config/homebrew, and have it be used/read by the brew command without having to explicitly set XDG_CONFIG_HOME.
I don't currently explicitly set XDG_CONFIG_HOME for any other tool I use on macOS or Linux, and most (or at least many) of them use ~/.config for config files.
I currently use a wrapper script for the brew command whose sole purpose is to set XDG_CONFIG_HOME before calling brew.

[MikeMcQuaid]

@etcusrvar Two questions:

• are you on macOS or Linux?
• why do you want to avoid setting XDG_CONFIG_HOME in your environment?

[carlocab]

This behaviour is similar to what tools like git do, so it seems fine to me.

[carlocab]

Suggested change

	elif [[ -d "${HOME}/Library/Application Support/homebrew" ]]
	then
	HOMEBREW_USER_CONFIG_HOME="${HOME}/Library/Application Support/homebrew"
	elif [[ -d "${HOME}/Library/Application Support/Homebrew" ]]
	then
	HOMEBREW_USER_CONFIG_HOME="${HOME}/Library/Application Support/Homebrew"

I think directories in ~/Library are usually capitalised.

[etcusrvar]

"usually" being the operative word. I do see a handful of directories on my system that aren't. I was aiming for consistency across homebrew options. But I'm fine with having it be capitalized there and lower case in other locations if we want.

[MikeMcQuaid]

Please hold on merging until we've discussed this a bit more.

[etcusrvar]

@etcusrvar Two questions:

• are you on macOS or Linux?

I believe I've answered that a few times in the comments here and in the linked issue-- yes. both.

• why do you want to avoid setting XDG_CONFIG_HOME in your environment?

Primarily because no other tool requires it to be explicitly set because I'm using the default of ~/.config.

Many other tools use ~/.config as their default location for config files without needing XDG_CONFIG_HOME being set, on both macOS and Linux. Homebrew is the only one I've come across where it's explicitly required to be set.

Here's the docs on configuration files for a few tools-- chezmoi, fish, git, helix, htop, mise, tmux.

Many of these and others follow the XDG spec, on both Linux and macOS. (And, yes, many don't. :( )

I'm fine with setting app specific environment variables, like HOMEBREW_*, if needed. But XDG_CONFIG_HOME is a standard that is used by many applications and tools, and it doesn't make sense to me to have to explicitly define it for only one tool, when I want to use the standard default location.

[MikeMcQuaid]

This is already handled by the else case.

[etcusrvar]

yes. The reason I did this this way was because I didn't want a user who might have both ~/.homebrew and one of the other 3 directories created to be surprised when their configuration suddenly changed. But I'm fine with only defining it once.

[MikeMcQuaid]

Ok, makes sense, thanks 👍🏻

[MikeMcQuaid]

Primarily because no other tool requires it to be explicitly set because I'm using the default of ~/.config.

Is it not set by the XDG environment on Linux? What desktop environment/Linux distribution are you using there?

Many of these and others follow the XDG spec, on both Linux and macOS. (And, yes, many don't. :( )

I do not think the XDG specification should be followed on macOS.

But XDG_CONFIG_HOME is a standard that is used by many applications and tools, and it doesn't make sense to me to have to explicitly define it for only one tool, when I want to use the standard default location.

Would setting HOMEBREW_CONFIG_HOME or similar be suitable instead?

Note that the behaviour and/or documentation for both brew bundle --global and HOMEBREW_LIVECHECK_WATCHLIST will need to be tested and updated based on any changes here.

As-is, I'm disinclined to add several new default directories based on one person/PR when it's already configurable. If it's insufficiently configurable: it would be preferable for me for HOMEBREW_CONFIG_HOME or similar to be configurable, default to ~/.homebrew or XDG_CONFIG_HOME if explicitly set.

[etcusrvar]

Is it not set by the XDG environment on Linux? What desktop environment/Linux distribution are you using there?

I've used Debian, Arch, and others, and none of the XDG_* vars are set by default, because they all have default locations if those vars are unset. Homebrew is not using the default location. In the homebrew/brew docker image that Homebrew provides, none of these variables are set.

I do not think the XDG specification should be followed on macOS.

Agreed. (But many tools do anyway, such as those I listed earlier.) And, as is, without this PR, I use a wrapper script with XDG_CONFIG_HOME defined on macOS, and it works fine, as expected, just as it does on Linux.

Would setting HOMEBREW_CONFIG_HOME or similar be suitable instead?

That would be great!

Note that the behaviour and/or documentation for both brew bundle --global and HOMEBREW_LIVECHECK_WATCHLIST will need to be tested and updated based on any changes here.

Agreed. This is an incomplete draft PR at this point, and is why I mentioned this earlier-- "If the idea meets with approval, I can add any appropriate tests and documentation."

As-is, I'm disinclined to add several new default directories based on one person/PR when it's already configurable. If it's insufficiently configurable: it would be preferable for me for HOMEBREW_CONFIG_HOME or similar to be configurable, default to ~/.homebrew or XDG_CONFIG_HOME if explicitly set.

Ok. The only change for me then as a user would be to explicitly define HOMEBREW_CONFIG_HOME instead of XDG_CONFIG_HOME, which is fine I suppose. It still would be nice if the standard default ~/.config was used.

[MikeMcQuaid]

The only change for me then as a user would be to explicitly define HOMEBREW_CONFIG_HOME instead of XDG_CONFIG_HOME, which is fine I suppose.

Yup, I think that's the best change here.

It still would be nice if the standard default ~/.config was used.

As long as we still pick up the .homebrew location if it's been already used: I would be fine with a ~/.config default on Linux as long as using .homebrew on Linux will both work and take priority over .config.

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