How add Evil keybindings to Magit, without removing all Magit prefix-keys

Question

In magit status of a Git repository, you usually press f u to fetch from upstream (these keybindings in Magit will call magit-fetch-from-upstream).

With Magit keybindings I have noticed the letters hkjl after prefix f were not used yet. So I added the following:

(map! :map magit-mode-map
 :n "fh" #'evil-window-left
 :n "fl" #'evil-window-right)

This works well in Magit. Later it turns out this also disabled the prefix-related keybinding u after prefix f. So I'm wondering how I could add another keybinding after prefix f while retaining the other Magit prefix-related keybindings?

Answer 1

Transients activate their own keymaps. The Modifying Existing Transients section of the transient manual describes how to extend existing transients. Unfortunately, it generally takes quite some investment to understand the transient manual.

Anyway, you could extend the 'magit-fetch prefix as follows:

(with-eval-after-load 'magit-fetch
  (transient-append-suffix
  'magit-fetch
  '(3)
  ["Navigate"
   ("h" "forward char" evil-backward-char :transient t)
   ("l" "backward char" evil-forward-char :transient t)]))

The second argument (3) defines where to add the extra commands.

The :transient t sets the transient to stay transient.

I am not sure how to 'point' Emacs to use the 'original' keymap if some key is not included in the prefix (I vaguely remember this was possible, but I can not find it again now... however, maybe I have dreamed it :).