No warning/error for files ignored due to capital letters in filename

[mach-diamond]

What Git revision are you using?

aiken v1.0.26-alpha+075668b

What operating system are you using, and which version?

• Linux / Ubuntu
• Linux / Other
• macOS
• Windows

Describe what the problem is?

Files with capital letters in the filename are ignored and no warning/error is provided if this is the intended behavior.

What should be the expected behavior?

A warning/error message indicating the file was ignored due to the capital letter or acceptance of files with capital letters in the filename.