How to skip a file extension from getting listed as Unstaged files in SourceTree

I am using Source Tree and I wanted to skip .project files from getting listed in the Unstaged files

1. Open up Source Tree
2. Select the feature that you are working on
3. Go to Tools --> Options --> Git 
4. Click on Edit File button corresponding to Global Ignore List

5. It will open the file gitignore_global in a editor
6. Add the following entry *.project and save the changes.