Allow RUFF_NO_CACHE environment variable (like RUFF_CACHE_DIR)

[akx]

Summary

Being able to set --no-cache without touching the command line makes comparing formatter speed with e.g. Hyperfine a lot easier; Black allows one to set BLACK_CACHE_DIR=/dev/null, but setting RUFF_CACHE_DIR=/dev/null has Ruff choke:

error: Failed to initialize cache at /dev/null: Not a directory (os error 20)
error: Failed to initialize cache at /dev/null: Not a directory (os error 20)
warning: Failed to open cache file '/dev/null/0.1.4/18160934645386409287': Not a directory (os error 20)

Alternately, we could make a /dev/null (or nul on Windows) cache directory imply --no-cache?

Test Plan

None yet.

[github-actions]

ruff-ecosystem results

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Linter (preview)

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[MichaReiser]

You can use --parameter-list and set e.g. CACHE to --no-cache or an empty string. That's how I did cached/uncached comparisons in the past. I'm not sure if that's more or less convenient than what you use.

I'm a bit hesitant from adding environment variables only for profiling. They are a source of confusion and introduce some complexity.