more lintcheck updates
* 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 :sweat_smile: )
* 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