How can I improve this Emacs lisp function? - emacs

Question

The intent is to use git grep as the command for M-x grep, and all the buffer benefits that come along with it. Desired functionality:
It reads the word/thing at point as the default value (done, sort of)
It reads the current region as the default argument if a region is set.
The following is the code I have so far:
(defun bw-read-string-at-point ()
(interactive)
(let ((word (word-at-point)))
(set-text-properties 0 (length word) nil word)
word))
(defun bw-git-grep (search-str)
"Uses `git-grep` to find `search-str`"
(interactive
(list
(read-string (format "Search for (%s): " (bw-read-string-at-point)))))
(let ((search-str (if (= (length search-str) 0)
(bw-read-string-at-point) search-str)))
(grep (concat "git --no-pager grep -i -I -nH --no-color --extended-regexp " search-str))))
I feel like the interactive bit there is quite clumsy and could be made much better.

Answer 1

Actually, it looks pretty good. Except you should use the default' argument ofread-string, and the interactive in bw-read-string-at-point should not be there. Or better yet, just use grep-tag-default.
Here's how I'd tweak it:
(defun bw-git-grep (search-str)
"Uses `git-grep` to find `search-str`"
(interactive
(let ((default (grep-tag-default)))
(list
(read-string (format "Search for (default %s): " default)
nil nil default))))
(grep (concat "git --no-pager grep -i -I -nH --no-color --extended-regexp " search-str)))

Answer 2

I would use read-from-minibuffer instead of read-string:
(defun bw-git-grep (pattern)
(interactive
(list
(read-from-minibuffer
"Search for: "
(if (region-active-p)
(buffer-substring-no-properties (region-beginning) (region-end))
(thing-at-point 'word)))))
(let* ((grep-command "git --no-pager grep -i -I -nH --no-color --extended-regexp ")
(command (concat grep-command pattern))
(grep-use-null-device nil))
(grep command)))
Also, you probably need to ensure that grep-use-null-device is nil to avoid grep appending /dev/null to your command (which git doesn't seem to like much)