Not possible to silence new lint about dbg in tests without editing tree

Summary

In our project we want to allow use of dbg! in tests. I filed issues about this #8481 and #8758 and kind contributors implemented my request. However, this turned out to be controversial - #8838. To deal with this a new configuration file item was introduced, allow-dbg-in-tests, #8897.

However, it is not possible to use this to re-allow dbg! in tests (which are allowed by stable clippy) in a project which wants to compile both with stable and nightly.

This is because stable clippy does not understand the new config option and rejects it; whereas unstable clippy hates dbg! in tests by default.

IMO the default fof allow-dbg-in-tests ought to be true. The rationale for forbidding dbg! does not apply to test code. That some people have a different opinion doesn't invalidate that.

However, there are also some underlying issues:

• clippy should tolerate (or at least, be capable of tolerating) unknown configuration options, so that the same file can generally be used with multiple versions
• It should be possible to specify an alternative config file location on the command line.
• It should be possible to specify configuration variables on the command line piecemeal.

Reproducer

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Version

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Additional Labels

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The issue centers on the allow-dbg-in-tests configuration and Clippy's handling of unknown options across stable and nightly versions. It also lists alternative configuration-file paths and piecemeal command-line configuration as related goals, but provides no files, tests, entry points, or concrete definition of done.