From f01dffe56c2e59791c357ed36b9f1113109b681e Mon Sep 17 00:00:00 2001
From: Kyle Meyer <kyle@kyleam.com>
Date: Wed, 12 Apr 2017 23:41:51 -0400
Subject: Add mode for reviewing diffs

---
 lisp/km-diff.el | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)

diff --git a/lisp/km-diff.el b/lisp/km-diff.el
index 9c2b143..9b92f7a 100644
--- a/lisp/km-diff.el
+++ b/lisp/km-diff.el
@@ -75,6 +75,96 @@
   (when km/ediff-previous-window-config
     (set-window-configuration km/ediff-previous-window-config)
     (setq km/ediff-previous-window-config nil)))
+
+;;; Diff review
+
+(defvar km/diff-review-mode-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map (kbd "C-w") #'km/diff-review-copy-comment)
+    map)
+  "Keymap for Diff Review mode.")
+
+(defvar km/diff-review-font-lock-keywords
+  '(("^:.*$" . 'font-lock-function-name-face)))
+
+;;;###autoload
+(define-minor-mode km/diff-review-mode
+  "Minor mode for reviewing diffs.
+
+When this mode is turned on
+
+  * `auto-fill-mode' is enabled
+
+  * the buffer is editable
+
+  * \":\" is set as the comment character
+
+  * typing \\<km/diff-review-mode-map>\\[km/diff-review-copy-comment] \
+will copy and the current comment,
+     minus the comment character"
+  nil
+  " DiffRev"
+  km/diff-review-mode-map
+  (if km/diff-review-mode
+      (progn
+        (auto-fill-mode)
+        (set (make-local-variable 'comment-start) ": ")
+        (setq fill-column (+ 2 fill-column))
+        (font-lock-add-keywords nil km/diff-review-font-lock-keywords)
+        (setq buffer-read-only nil)
+        (if (not diff-update-on-the-fly)
+            (remove-hook 'write-contents-functions 'diff-write-contents-hooks t)
+          (remove-hook 'after-change-functions 'diff-after-change-function t)
+          (remove-hook 'post-command-hook 'diff-post-command-hook t)))
+    (font-lock-remove-keywords nil km/diff-review-font-lock-keywords)
+    (diff-mode))
+  (when font-lock-mode
+    (font-lock-flush)))
+
+(defun km/diff-review-copy-comment ()
+  (interactive)
+  (if (or (use-region-p)
+          (not (eq ?: (char-after (point-at-bol)))))
+      (call-interactively #'kill-region)
+    (let ((beg (save-excursion (goto-char (point-at-bol))
+                               (if (bobp)
+                                   (point)
+                                 (while (and (eq ?: (char-after))
+                                             (not (bobp)))
+                                   (forward-line -1))
+                                 (forward-line)
+                                 (point))))
+          (end (save-excursion (goto-char (point-at-bol))
+                               (while (and (eq ?: (char-after))
+                                           (not (eobp)))
+                                 (forward-line 1))
+                               (forward-line -1)
+                               (point-at-eol))))
+      (message
+       "%s"
+       (kill-new
+        (thread-last
+            (buffer-substring-no-properties beg end)
+          (replace-regexp-in-string "^: ?" "")
+          (replace-regexp-in-string "\\`\\s-+" "")
+          (replace-regexp-in-string "\\s-+\\'" "")))))))
+
+(defun km/diff-review-as-mail ()
+  (interactive)
+  (let ((contents (buffer-substring-no-properties (point-min) (point-max))))
+    (with-current-buffer (get-buffer-create "*Diff Review Mail*")
+      (erase-buffer)
+      (insert contents)
+      (goto-char (point-min))
+      (while (not (eobp))
+        (insert "> ")
+        (forward-line 1))
+      (goto-char (point-min))
+      (while (re-search-forward "> : ?" nil t)
+        (replace-match ""))
+      (message-mode)
+      (set-buffer-modified-p nil)
+      (pop-to-buffer (current-buffer)))))
 
 (provide 'km-diff)
 ;;; km-diff.el ends here
-- 
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