Paths may change to lowercase in explorer

What steps will reproduce the problem?

1. checkout a branch of a repository with some committed files in a path with mixed case
2. alter 1 file so File Explorer shows a red exclamation mark instead of a green check
3. close and open File Explorer (don't know if this is necessary), path should show correct case: repo_name/DirOne/DirTwo/DirThree/DirFour/File
4. right click on the red exclamation marked file, select Tortoise Git, select diff
5. click a window of another app and the first 2 directory levels below the name of the repository change to lower case: repo_name/dirone/dirtwo/DirThree/DirFour/File
6. further use of the git menu options does not work unless Explorer is closed and opened again

What is the expected output? What do you see instead?

Step 5 should not have resulted in a change of case in the path.

What version of TortoiseGit and Git are you using? On what operating system?

Tortoise 1.8.16.0 Git 1.9.5.msysgit.1 Windows 7. SP-1. 64-bit.

Please provide any additional information below.

Related to Issue #2559 (closed).