1. Create a new project: "C/C++ Application", with all defaults
2. In Projects navigation tree, rename "Makefile" to "foo.bar"
Expected:
 - Physical file renamed to "foo.bar"
 - Element in project list to change to "foo.bar"
Result:
 - Physical file renamed to "foo.bar" (Correct result)
 - Element in project list changed to "foo" (Wrong result)

3. Similar problem happens if you re-add the read file "foo.bar" to the project
4. Rename "foo.bar" to "foo.mk"
Expected:
 - Physical file renamed to "foo.mk"
 - Element in project list to change to "foo.bar"
Result:
 - Physical file renamed to "foo.mk" (Correct result)
 - Element in project list remains "foo.bar" (Wrong result)

I was playing around with other combinations of renaming files, and I feel there were some other cases that generated these same bad behaviors. However I have been unable to reproduce these others cleanly.

However, once the file has a '.mk' file extension, it's stuck that way (which is normal behavior that I'm not a fan of: #122190) and the bad behaviors described don't happen anymore.

I have not explored what impact this has on versioning systems. Questions like "Does this rename the file according to the physical file or the element still in the tree in git's staged changes?"

I have also not explored if this happens when you have other files in a project that do not have file extensions, and you add one. Or change from an unrecognized extension to a known one. Or if this happens in projects other than C/C++ ones.