New deletion command

init.el

@@ -315,6 +315,36 @@ Apply OLDFUN with to ARGS."
                                 . conf-mode))
 (add-to-list 'auto-mode-alist `(,(rx (or bos "/") "README" eos) . markdown-mode))
 
+(defun my/delete-backward-char-or-tab (n &optional killflag)
+  "Delete N characters, or that many characters worth of tabs, before point.
+If there is only whitespace between point and the beginning of the current line,
+delete N characters worth of tabs, rounding up.  For example, if N is 2 and
+`tab-width' is 4, delete one tab.  If `indent-tabs-mode' is nil, instead delete
+`tab-width' spaces.  In this case, deletion stops at the beginning of the
+current line.
+
+If point is anywhere else on the line, delete N characters.
+
+If KILLFLAG is non-nil, save the deleted text to the kill ring."
+  (interactive "p\nP")
+  (unless (natnump n)
+    (signal 'wrong-type-argument (list 'natnump n)))
+  (cl-flet ((only-indentation-p ()
+              (let ((start (point)))
+                (save-excursion
+                  (beginning-of-line)
+                  (skip-syntax-forward " " start)
+                  ;; `back-to-indentation' does this, so I do too
+                  (backward-prefix-chars)
+                  (>= (point) start))))
+            (count-chars-for-delete-tab ()
+              (min (* (ceiling n tab-width) (if indent-tabs-mode 1 tab-width))
+                   (- (point) (pos-bol)))))
+    (if (not (only-indentation-p))
+        (delete-char (- n) killflag)
+      (delete-char (- (count-chars-for-delete-tab)) killflag))))
+(keymap-set prog-mode-map "DEL" #'my/delete-backward-char-or-tab)
+
 ;; Show the fill column
 ;; (global-display-fill-column-indicator-mode -1)
 ;; (setopt display-fill-column-indicator-warning t)