Magit, delete-trailing-whitespace on hunk under point.

jorbi-magit.el

(defun jorbi-magit/-line-region-of-section-at-point ()
  "If point is in a hunk return a list of info about the hunk.

The info is like (expanded-file-name starting-line number-of-lines-show)"
  (let* ((section (magit-current-section))
         (context-type (magit-section-context-type section)))
    (when (and (member 'hunk context-type))
      (let* ((info
              (mapcar 'string-to-number
                      (split-string
                       (second (split-string
                                (magit-section-info
                                 (magit-current-section))
                                "[ @]" t))
                       ",")))
             (start-line (car info))
             (line-count (or (and (cdr info) (cadr info)) 1)))
        (let ((parent (magit-section-parent section)))
          (while (and parent
                      (not (equal (magit-section-type parent)
                                  'diff)))
            (setq magit-section-parent parent))
          (list (expand-file-name (magit-section-info parent))
                start-line
                line-count))))))

(defun jorbi-magit/delete-hunk-trailing-whitespace ()
  "Run `delete-trailing-whitespace' on the region shown in the unstaged hunk under point.
The cooresponding file will be saved and the magit-status buffer will be refreshed."
  (interactive)
  (let ((area (jorbi-magit/-line-region-of-section-at-point)))
    (if (and area (member 'unstaged (magit-section-context-type (magit-current-section))))
        (progn
          (destructuring-bind (file start-line total-lines) area
            (with-current-buffer (find-file-noselect file)
              (save-some-buffers)
              (save-excursion
                (delete-trailing-whitespace
                 (progn (goto-char (point-min))
                        (forward-line (1- start-line))
                        (point-at-bol))
                 (progn (forward-line (1- total-lines))
                        (point-at-eol))))
              (save-buffer)))
          (magit-refresh))
      (message "Must be in a unstaged magit hunk."))))


;; setup a key binding
;; (define-key magit-status-mode-map (kbd "C-c s d") 'jorbi-magit/delete-hunk-trailing-whitespace)