Starting Git 2.0.1 (June 25th, 2014), a git mv will just work on a case-insensitive OS.
See commit baa37bf by David Turner (dturner-tw).
mv: allow renaming to fix case on case-insensitive filesystems
“git mv hello.txt Hello.txt” on a case-insensitive filesystem always triggers “destination already exists” error, because these two names refer to the same path from the filesystem’s point of view and requires the user to give “--force” when correcting the case of the path recorded in the index and in the next commit.
Detect this case and allow it without requiring “
--force“.
git mv hello.txt Hello.txt just works (no --force required anymore).
The other alternative is:
git config --global core.ignorecase false
And rename the file directly; git add and commit.
It does work in a CMD. It might fail in a git bash (on Windows) session (see Louis-Caron’s answer)
As noted by jaquinocode in the comments, if your local repository itself has that setting:
git config --local core.ignorecase false