Feature: Add CACHEDIR.TAG to zig-cache

[Ciantic]

Consider adding CACHEDIR.TAG to zig-cache directory.

It's just text file with ASCII text at the beginning:

Signature: 8a477f597d28d172789f06886806bc55

(The hexadecimal string is same on all CACHEDIR.TAG files.)

For example Rust does this, and plenty other things, it makes easier for backup tools to ignore the directory.

[daurnimator]

Do you have examples of tools that use CACHEDIR.TAG? this is the first I've heard of it.

[g-w1]

Cargo uses it.

[mikdusan]

Do you have examples of tools that use CACHEDIR.TAG? this is the first I've heard of it.

from gnutar docs:

       --exclude-caches
              exclude contents of directories containing CACHEDIR.TAG, except for the tag file itself

       --exclude-caches-all
              exclude directories containing CACHEDIR.TAG

       --exclude-caches-under exclude everything under directories containing
              CACHEDIR.TAG

[Ciantic]

Kopia (my preferred backup tool at the moment) uses it by default

[perillo]

Do you have examples of tools that use CACHEDIR.TAG? this is the first I've heard of it.

Restic and fontconfig supports it. I also opened an issue for rsync.

[perillo]

What about adding CACHEDIR.TAG to the zig-out directory, too?