Add gptel-chat-with-buffer function and keybinding

This commit introduces the gptel-chat-with-buffer function, allowing users to start a chat with the buffer content. It also updates keybindings, assigning "b" to the new function and moving gptel-select-backend to "B".

emacs/.emacs.d/config/init-ai.el

@@ -57,6 +57,17 @@
       (gptel buffer nil initial interactivep))
     (with-current-buffer buffer
       (setq-local gptel--system-message (alist-get 'org-mode gptel-directives))))
+  (defun gptel-chat-with-buffer (&optional arg interactivep)
+    (interactive (list current-prefix-arg t))
+    (let* ((name (format "*gptel: %s*"(buffer-name)))
+           (buffer (if arg
+                       (generate-new-buffer name)
+                     name)))
+      (gptel buffer nil (buffer-string) interactivep)
+      (with-current-buffer buffer
+        (goto-char (point-max))
+        (newline)
+        (insert (gptel-prompt-prefix-string)))))
   :general
   ("C-c RET" #'gptel-send
    "C-c C-<return>" #'gptel-menu)
@@ -65,7 +76,8 @@
    "o" #'gptel-org
    "s" #'gptel-send
    "m" #'gptel-menu
-   "b" #'gptel-select-backend
+   "b" #'gptel-chat-with-buffer
+   "B" #'gptel-select-backend
    "a" #'gptel-context-add
    "f" #'gptel-context-add-file
    "k" #'gptel-abort))