parse a git diff enough to learn useful stuff

(defun git-draft/diff ()
  "Diff the git index and parse the result."
  (reverse
   (let (result)
     (with-temp-buffer
       (let ((pager (getenv "GIT_PAGER")))
         (setenv "GIT_PAGER" "")
         (unwind-protect
              (shell-command "git diff -U --cached ." (current-buffer))
           (when pager 
             (setenv "GIT_PAGER" pager))))
       (goto-char (point-min))
       (while (re-search-forward 
               (rx (or (and line-start ; diff start
                            (group-n 1 "diff --git ") 
                            "a/" (group-n 2 (1+ (any "a-zA-Z0-9._-"))) " "
                            "b/" (group-n 3 (1+ (any "a-zA-Z0-9._-")))
                            line-end)
                       (and line-start  ; hunk start
                            (group-n 1 "@@ -")
                            (group-n 2 (1+ (any "0-9")))
                            "," (group-n 3 (1+ (any "0-9")))
                            " +" (group-n 4 (1+ (any "0-9")))
                            (* (and "," (group-n 5 (1+ (any "0-9")))))
                            " @@"  (* not-newline) line-end)))
               nil t)
         (if (equal (match-string 1) "@@ -")
             (push (list :hunk
                         :from-start (match-string 2)
                         :from-count (match-string 3)
                         :to-start (match-string 4))  result)
             ;; Else it's a diff start
             (push (list :file
                         :from (match-string 2)
                         :to (match-string 3)) result)))
       result))))

Sat Jul 26 22:38:05 2014