Wrapper for Emacs' default grep. It uses `git grep`, passes in the git project directory, and also uses the current symbol under cursor as a default.

cjw_grep.el

(defun cjw-git-grep (my-word)
  "Use git-grep for search in current project (vc-root-dir). Default
search term uses symbol under cursor"
  (interactive
   (list
    (read-string
     (format "Search (%s): " (thing-at-point 'symbol)) ; prompt
     nil ; initial input
     nil ; history list
     (thing-at-point 'symbol) ; evaluated. will be default
     )))
  (let ((default-directory (vc-root-dir)))
    (message "=====> git grep '%s' in %s" my-word (vc-root-dir))
    (grep (format "git --no-pager grep --line-number -e '%s'" my-word))))