change detail for commits before double renaming not viewable

This issue can be repeated using the git repo as attached. The repo contains two renaming operations on a file named a.txt. using "gitk --follow -p new_folder/a.txt" shows me the correct history with change details for all the involved commits.

Steps to repeat based on the attached git repo with uncommitted changes:

1. Download and unzip
2. open in SourceTree
3. Click "History"
4. Click "Uncommitted changes"
5. Right click on "new_folder/a.txt" in "Unstaged files"
6. In the newly opened window for viewing history of "new_folder/a.txt", check "Follow renamed files"
7. We can see three commits
8. Click and check what's on the right side commit by commit from top to bottom on the left side, when comes to the commit messaged "added a.txt", nothing is shown on the right side.