Variable: ff-case-fold-search
ff-case-fold-search is a customizable and buffer-local variable
defined in find-file.el.gz.
Documentation
Non-nil means ignore cases in matches (see case-fold-search).
If you have extensions in different cases, you will want this to be nil.
Source Code
;; Defined in /usr/src/emacs/lisp/find-file.el.gz
(defcustom ff-case-fold-search nil
"Non-nil means ignore cases in matches (see `case-fold-search').
If you have extensions in different cases, you will want this to be nil."
:type 'boolean
:local t)