Deno: store cache files in recommended standard location

[abdulkareemnalband]

I'm psyched about deno
I like decentralized library , sandbox by default

Just some nitpick

Instead of polluting home directory with ~/.deno

Use XDG Base Directory Specification for linux

Use Mac OS specific locations https://developer.apple.com/library/archive/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/MacOSXDirectories/MacOSXDirectories.html#//apple_ref/doc/uid/TP40010672-CH10-SW1

[KeKsBoTer]

IMO for windows you should use %localappdata%/deno as cache directory.

[flying-sheep]

We should use the directories crate:

```rust
use directories::ProjectDirs;

let cache_dir = match ProjectDirs::from("land", "ry", "deno") {
Some(proj_dirs) => proj_dirs.cache_dir(),
None => // fallback to ~/.deno
}

[bartlomieju]

You can control location of deno directory with DENO_DIR. Check out this article for more info.

CC @ry

[abdulkareemnalband]

@bartlomieju It's not about configuring ENVIRONMENT , but playing nicely with current conventions, and out box experience

[flying-sheep]

That, and DENO_DIR sounds like it’s not exclusively for caches. If deno at some point does something else with it than storing its history and cache files in it, it won’t be sufficient anymore, as the cache dir isn’t equal to e.g. the config dir.

OSs have standards for directories. There’s crates implementing those standards. The standards are there because e.g. cache dirs don’t need to be backed up and can be cleaned on low disk space. So they need to be followed.