lint command paths argument is unexpectedly case sensitive when applying exclude rules

swiftlint lint [] [ ...]

If my code is held in /home/a/b/c and I pass in the argument /home/a/b/C then SwiftLint scans the directory /home/a/b/c/.

That's cool, and expected. it's a Mac, it's not case sensitive.

BUT. If my config.yml file contains an exclusion rule:

excluded: # paths to ignore during linting.
  - build

😀 then the exclusion works when the invocation looks like this:

swiftlint lint --config config.yml /home/a/b/C

😡 but the exclusion is not honored in this case:

swiftlint lint --config config.yml /home/a/b/C

and then my /home/a/b/c/build directory gets scanned, with horrible errors as a result.

Reproduce:

Death-Star:myCode apple$ pwd
/tmp/myCode
Death-Star:myCode apple$ find . -print -exec cat '{}' ';'
.
cat: .: Is a directory
./lint.yml
excluded: # paths to ignore during linting.
  - badCode
./1.swift
if a =  3 {
  print("hi")
}
./badCode
cat: ./badCode: Is a directory
./badCode/bad.swift
if a =  3 {
  print("hi")
}
Death-Star:myCode apple$ swiftlint --config lint.yml /tmp/myCode/
Linting Swift files at paths /tmp/myCode/
Linting '1.swift' (1/1)
Done linting! Found 0 violations, 0 serious in 1 file.
Death-Star:myCode apple$ swiftlint --config lint.yml /tmp/MYCODE/
Linting Swift files at paths /tmp/MYCODE/
Linting '1.swift' (1/2)
Linting 'bad.swift' (2/2)
Done linting! Found 0 violations, 0 serious in 2 files.
Death-Star:myCode apple$ 

Start by reproducing the case-sensitive path behavior with the swiftlint lint commands and the lint.yml or config.yml exclusion rule shown in the issue. Trace how the lint entry point resolves paths and applies exclusions; done means the excluded badCode or build directory is skipped for both correctly and incorrectly cased invocation paths.