Tab not working in SSH-Deploy-Diff buffer

[rda716]

Pressing TAB displays message "Buffer is read-only: #<buffer *SSH Deploy diff*>".

Pressing C-h k TAB shows the key is bound to indent-for-tab-command

Running GNU Emacs 26.3 on Ubuntu 20.04.3 LTS.

Configuration:

(use-package ssh-deploy
  :ensure t
  :demand
  :bind-keymap
  ("C-c d" . ssh-deploy-prefix-map)
  :hook ((after-save . ssh-deploy-after-save)
         (find-file . ssh-deploy-find-file))
  :config
  (ssh-deploy-line-mode))

[cjohansson]

Do you have the cursor at a filename?