Cache handling

[darkdragon-001]

Optimized cache management is important to keep cloud storage costs under control.

I would like to use --cache-dir for all operations. Having this built-in makes sure I don't forget it for any command.

The other options like --with-cache/--no-cache can be specified via -- --option if you don't want to add official support.

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Furthermore, behavior different from restic default should be documented:

runrestic/runrestic/restic/tools.py

Lines 89 to 92 in 7622739

	if os.geteuid() == 0: # pragma: no cover; if user is root, we just use system cache
	os.environ["XDG_CACHE_HOME"] = "/var/cache"
	elif not (os.environ.get("HOME") or os.environ.get("XDG_CACHE_HOME")):
	os.environ["XDG_CACHE_HOME"] = "/var/cache"

[andreasnuesslein]

I thank you for all your comments. You clearly know what you're talking about.

Would you mind create a PR or two for some of the suggestions you're making?

Cheers

[darkdragon-001]

How should it go in the config file?

[andreasnuesslein]

So according to restic, it should work to just set XDG_CACHE_DIR because all restic commands seem to honor that. However I know I put in logic that is thwarting that at the moment. So I suggest we throw out the custom if os.geteuid() == 0: logic. Next we recommend setting XDG_CACHE_DIR in [environment] in the docs and lastly print a warning on running runrestic when no explicit XDG_CACHE_DIR is set to let the user know what runrestic assumes then.
i.e.: [warning] You have not explicitily set XDG_CACHE_DIR. Falling back to /var/cache/

[darkdragon-001]

I just noticed RESTIC_CACHE_DIR environment variable is also supported. So this can just be used in the config environment section if the user wants to use it! Therefore, I would just remove this code block...

I suggest to add a warning right now that the behavior will change in a future version when one of the quoted code blocks is executed. And then just remove this code in the next bigger update.

I added an issue to get a complete list of environment variables in restic/restic#2763.

[darkdragon-001]

You can pass env to subprocess.Popen().

I suggest the following:

env = { name: os.environ[name] for name in ['HOME','XDG_CACHE_DIR','TMPDIR'] if name in os.environ }
env = { **env, **config['environment'] }