git-grep.el

;; There's something similar (but fancier) in vc-git.el: vc-git-grep
;; -I means don't search through binary files
(defcustom git-grep-switches "--extended-regexp -I -n --ignore-case"
  "Switches to pass to `git grep'."
  :type 'string)

(defcustom git-grep-default-work-tree (expand-file-name "~/Documents/src/kits")
  "Top of your favorite git working tree.  \\[git-grep] will search from here if it cannot figure out where else to look."
  :type 'directory
  )

(when (require 'vc-git nil t)

  ;; Uncomment this to try out the built-in-to-Emacs function.
  ;;(defalias 'git-grep 'vc-git-grep)

  (defun git-grep (command-args)
    (interactive
     (let ((root (vc-git-root default-directory)))
       (when (not root)
         (message "git-grep: %s doesn't look like a git working tree; searching from %s instead" default-directory git-grep-default-work-tree)
         (setq root git-grep-default-work-tree))
       (list (read-shell-command "Run git-grep (like this): "
                                 (format (concat
                                          "cd %s && "
                                          "git grep %s -e %s")
                                         root
                                         git-grep-switches
                                         (shell-quote-argument (thing-at-point 'symbol)))
                                 'git-grep-history))))
    (let ((grep-use-null-device nil))
      (grep command-args))))