$ mv 'Assignments' 'assignments' mv: cannot move `Assignments' to a subdirectory of itself, `assignments/Assignments'
Trying to rename
Assignments directory to
The OSX HFS+ filesystem is case-insensitive, so it's interpreting
you are working with a filesystem which is not case sensitive (though it is case preserving). So when you say
The nuclear option is to start from scratch on this hard drive partition and OS installation by enabling OS X's Mac OS Extended (Journaled, case-sensitive) option. Be aware that this requires a complete reformatting of the disk and will clobber everything on the affected partition.
Another caveat is that certain applications in OS X do not place nicely with case-sensitive file systems. (At the time of this writing, I believe Steam is one of them.)
I just wanted to make readers of this question aware that this option does exist.
I personally resist the idea of the intermediary step and prefer to use the Finder to make such a change. It will not complain about the change if you rename the folder or file by just changing case.