Symptoms

When a file has been renamed and only the case has been modified, SourceTree will not reflect this change in it's UI on Mac OS. 

Diagnosis

Running a 'git status' will show nothing when you rename a file just for case, and therefore SourceTree does the same. 

Cause

The default Mac OS filesystem HFS+ is generally case insensitive. ABC.txt and abc.txt are considered the same file, unlike Linux.

Resolution

To workaround thisyou can use a temporary file to force the update.

For example if you want to change the case of "kh.png" to "KH.png" you would go to your Git repo from command line and do:

mv kh.png temp.png
git add -A
git commit -m "renaming kh.png to KH.png"
mv temp.png KH.png
git add -A
git commit --amend -m "Renamed file.txt to File.txt"