open-git-diff.el

(defun my:chomp (str)
  (replace-regexp-in-string "[\n\r]+$" "" str))

(defun my:git-project-p ()
  (string=
   (my:chomp
    (shell-command-to-string "git rev-parse --is-inside-work-tree"))
   "true"))

(defun my:tmux-do-command-for-file (filepath command)
  (progn
    (shell-command
     (format "tmux new-window 'cd %s; %s -- %s'"
             (file-name-directory filepath)
             command
             (file-name-nondirectory filepath)))))

(defun my:tmux-do-command-in-git-project (command)
  (if (my:git-project-p)
      (my:tmux-do-command-for-file buffer-file-name command)
    (progn
      (message "not in git repository.")
      nil)))

(defun my:open-iterm ()
  (shell-command (format "open -a iTerm")))

(defun my:git-diff-current-file ()
  (interactive)
  (if (my:tmux-do-command-in-git-project "git diff")
      (my:open-iterm)))

(defun my:tig-blame-current-file ()
  (interactive)
  (if (my:tmux-do-command-in-git-project "tig blame")
      (my:open-iterm)))