check $XDG_DATA_DIRS for a cache when user cache misses

[Managor]

As was requested in tldr-pages/tldr#19775

The method I implemented this with feels stupid but I guess it works.

[Managor]

Gotta write documentation before merging this

[acuteenvy]

Who is this for if we aren't going to include /usr/share/tldr in the client spec? I think a configuration option to change the cache location would be much more useful. /usr/share/tldr won't exist 99% of the time, because the user has to create that directory and extract the pages archive there. If someone is willing to do that, setting a config option shouldn't be a problem at all.

[Managor]

In my opinion just having the files exist would be less friction for the user or the deployer. Both cases would require /usr/share/tldr to exist, but the other one would need an extra step.

[acuteenvy]

just having the files exist would be less friction for the user

I'm not sure I understand what you're saying. How are these files going to exist? Do you want Linux distributions to package /usr/share/tldr?

[Managor]

A distribution can, but I'm not insisting on it. Personally it'll help me make easily copyable containers with a cache pre-downloaded.

Also as @SpikeTheDragon40k said here, it'll be great for airgapped systems. tldr-pages/tldr#19775 (comment)

[acuteenvy]

A distribution can, but I'm not insisting on it

I doubt anyone will if we keep this as a client-specific feature. And if it isn't standardized, why force users to use /usr/share/tldr?

I don't want to block this though, maybe it's just me. But if it's going to be client-specific, I'd personally rather have an environment variable to configure the location.

[SpikeTheDragon40k]

Could we use opt/tldr?

[Managor]

Possibly. Can you run me through the conceptual differences between using these directories? I always forget them.

[Managor]

I doubt anyone will if we keep this as a client-specific feature. And if it isn't standardized, why force users to use /usr/share/tldr?

I was thinking something similar, but @niklasmohrin convinced me otherwise that it would be too big of a shift in the goals of the spec. tldr-pages/tldr#19775 (comment)

We'll just have to rely on organic co-ordination instead of top-down dictating.

[SpikeTheDragon40k]

Possibly. Can you run me through the conceptual differences between using these directories? I always forget them.

Used Ai just to help me put the thought in words:

/usr/share is the standard spot for read-only, architecture-independent system data like docs and pages managed by your distro's package manager, think tldr pages installed via apt that auto-update and serve all users.

/opt is for optional, third-party or manually installed software packages kept in self-contained subdirs (like /opt/tldr) to avoid messing with the core system files.

The big diff: /usr/share stays pristine under OS control; /opt gives you isolation for custom stuff without conflicts.

[Managor]

Oh wait, wouldn't /usr/local/share drive the same purpose. If I remember correctly while testing different ways of implementing this, it was part of $XDG_DATA_DIRS. Maybe I should refactor this patch to loop through all of the entries in that variable.

[Managor]

Man the code is so goddamn inefficient. There's so many repeated operations. Complete rewrite would be great.