new: add a dwim function for viewing diff

* text-conf.el (durand-diff-dwim): Either diff with file or vc-diff,
  depending on whether the buffer is modified, whether the file is
  associated with a registered file, whether the argument is (list
  16).

(global-map): Bind to the global map.

1 files changed, 21 insertions, 0 deletions

diff --git a/text-conf.el b/text-conf.el
index c25a2bf..a035593 100644
--- a/text-conf.el
+++ b/text-conf.el
@@ -124,5 +124,26 @@ If ARG is non-nil, use a more verbose format."
 
 (define-key global-map (vector ?\H-=) #'durand-insert-timestamp)
 
+;; a diff-dwim
+
+;;;###autoload
+(defun durand-diff-dwim (&optional arg)
+  "Run `diff-buffer-with-file' or `vc-diff'."
+  (interactive "P")
+  (cond
+   ((and (or (not (buffer-modified-p))
+             (equal arg (list 16)))
+         (vc-registered (buffer-file-name)))
+    (vc-diff arg t))
+   ((buffer-modified-p)
+    (diff-buffer-with-file
+     (cond
+      (arg (read-buffer "Choose a buffer to diff: "
+                        (current-buffer) t))
+      ((current-buffer)))))
+   ((user-error "No reasonable way to diff"))))
+
+(define-key global-map (vector ?\C-\M-=) #'durand-diff-dwim)
+
 (provide 'text-conf)
 ;;; text-conf.el ends here.