Fix bug with getting parent directories in lookup_conf_file

[beetrees]

Currently lookup_conf_file doesn't canonicalize the configuration directory before using PathBuf::pop to get the parent directory. This isn't usually an issue when clippy is invoked via cargo clippy as CARGO_MANIFEST_DIR is already canonicalized. However, this currently causes clippy-driver to ignore any clippy.toml in any parent directories when CARGO_MANIFEST_DIR and CLIPPY_CONF_DIR are not set.

changelog: Fix a bug that would cause parent directories not to be searched for clippy.toml when using clippy-driver directly.

[rustbot]

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[giraffate]

@bors r+

It looks good, thanks!

[bors]

📌 Commit 3b22352 has been approved by giraffate

It is now in the queue for this repository.

[bors]

⌛ Testing commit 3b22352 with merge 73e412b...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: giraffate
Pushing 73e412b to master...