Changing case of Folder via Git bash on Windows

Make sure to close Visual Studio and any Windows Explorer folders related to that path.

In summary of the comments, you'll have to rename the directory via a intermediate temporary name. E.g.

git mv controller Controller-tmp
git mv Controller-tmp Controller

I think this has to do with the fact that the MinGW implementation of rename(2) does not support this operation. See this thread, the MSDN docs on the CRT rename implementation and those of the MoveFileEx function.