more lintcheck updates

[matthiaskrgr]

• do some refactoring and renaming here and there
• add comments to functions
• fix bug where git repos would not get checked out to the proper commits (cmd was not actually run in repo directory 😅 )
• print warnings if we can't clone or check out a git repo
• filter out noise from cargo-metadata errors and lint messages that contained absolute file paths (these would change with every pinned-nightly bump, polluting the logs)

changelog: more lintcheck refactoring and fixes for git crates

[rust-highfive]

r? @llogiq

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[matthiaskrgr]

r? @flip1995

[flip1995]

@bors r+

Thanks!

---

I had the idea this morning, to add a configuration option to a crate source, that lets you specify lint levels that should be passed over command line. If not provided the default all+pedantic is used.

[bors]

📌 Commit a95c250 has been approved by flip1995

[bors]

⌛ Testing commit a95c250 with merge f28c54c...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing f28c54c to master...