Finish the dired setup and its documentation

* Describe a dired based work-flow for inserting image file org-mode
  links.
* Finish the dired and wdired customization.
* Add dired key-bindings to open files in eww and to copy marked files
  to local or remote directories by means of rsync.

README.org

@@ -342,6 +342,30 @@ background.
 :CUSTOM_ID: sec:file-manager
 :END:
 
+[[info:emacs#Dired][Dired (info)]] and the [[https://github.com/ranger/ranger#readme][ranger]] file manager offer similar capabilities for copying,
+deleting, opening, renaming, and viewing files and directories, but the
+integration of [[info:emacs#Dired][dired (info)]] in Emacs is obviously much better than the
+integration of [[https://github.com/ranger/ranger#readme][ranger]] in Emacs.
+
+For instance, this setup allows to insert an =org-mode= link to an poorly
+identified file containing a specific image into an =org-mode= buffer by means
+of the facilities of [[info:emacs#Dired][dired (info)]] as follows:
+1. Type {{{kbd(C-x d)}}} to open the directory containing the pooly identified
+   file with the specific image in a =dired-mode= buffer.
+2. Start searching for the specific image by navigating to the name of any image
+   file.
+3. Type {{{kbd(v)}}} to switch to view the file in an =image-mode= buffer.
+4. In the =image-mode= buffer, continue searching for the specific image by
+   typing:
+   - {{{kbd(n)}}} to view the next image in the =dired-mode= buffer,
+   - {{{kbd(p)}}} to view the previous image in the =dired-mode= buffer, and
+   - {{{kbd(q)}}} to quit the =image-mode= buffer and to go back to the
+ =dired-mode= buffer.
+5. After finding the specific image, use {{{kbd(C-c l)}}} in the =image-mode=
+   buffer or the =dired-mode= buffer to store the =org-link=.
+6. Switch to the =org-mode= buffer and use {{{kbd(C-c C-l)}}} to insert the
+ =org-link= into the buffer.
+
 Listing [[lst:customize-dired]] makes the directory editor sort entries
 alphabetically after grouping the directories before grouping the files by
 extension.
@@ -352,6 +376,7 @@ extension.
 #+begin_src emacs-lisp
   (with-eval-after-load 'dired
     (custom-set-variables
+     '(dired-dwim-target t)
      ;; | switch | action                                 |
      ;; |--------+----------------------------------------|
      ;; | -a     | also list hidden entries               |
@@ -359,15 +384,71 @@ extension.
      ;; | -X     | sort alphabetically by entry extension |
      ;; | -G     | skip long listing format group names   |
      ;; | -1     | list one entry per line                |
-     '(dired-listing-switches "-alGX1 --group-directories-first")))
+     '(dired-listing-switches "-alGX1 --group-directories-first")
+     '(dired-recursive-copies 'always)
+     '(dired-recursive-deletes 'always)))
 
   (with-eval-after-load 'files
     (custom-set-variables
      ;; Ensure the use of `GNU-ls' from `coreutils' on darwin.
      '(insert-directory-program (or (executable-find "gls")
                                     (executable-find "ls")))))
+
+  (with-eval-after-load 'wdired
+    (custom-set-variables
+     '(wdired-allow-to-change-permissions t)))
 #+end_src
 
+Listing [[lst:extra-dired-key-bindings]] adds new key-bindings to =dired-mode-map= to:
+1. Open files with the [[https://en.wikipedia.org/wiki/Eww_(web_browser)][Emacs Web Wowser]] inside Emacs.
+2. Let [[https://en.wikipedia.org/wiki/Rsync][rsync]] copy marked files outside Emacs to a local or remote directory.
+The link [[https://truongtx.me/tmtxt-dired-async.html][asynchoronous execution library for Emacs Dired]] is the original source
+for the idea of using [[https://en.wikipedia.org/wiki/Rsync][rsync]] and the blog articles [[https://oremacs.com/2016/02/24/dired-rsync/][using rsync in dired]] and
+[[https://vxlabs.com/2018/03/30/asynchronous-rsync-with-emacs-dired-and-tramp/][asynchronous rsync with Emacs, dired and tramp]] are vivid recommendations written
+by experienced Emacs users.
+
+#+caption[Extra =dired= key bindings]:
+#+caption: Extra =dired= key bindings.
+#+name: lst:extra-dired-key-bindings
+#+begin_src emacs-lisp
+  (with-eval-after-load 'dired
+    (define-key
+      dired-mode-map (kbd "E")
+      (defun my-dired-eww-find-file ()
+        "Visit dired file with eww."
+        (interactive)
+        (eww-open-file (dired-get-file-for-visit))))
+
+    ;; https://truongtx.me/tmtxt-dired-async.html
+    (define-key
+      dired-mode-map (kbd "Y")
+      (defun my-dired-rsync (target)
+        "Copy marked files with `rsync' to TARGET directory."
+        (interactive
+         (list (expand-file-name
+                (read-file-name "Rsync to:" (dired-dwim-target-directory)))))
+        ;; Store all marked files into the `files' list and intialize
+        ;; the `rsync-command'.
+        (let ((files (dired-get-marked-files nil current-prefix-arg))
+              (rsync-command "rsync -av --progress "))
+          ;; Add all marked files as arguments to the `rsync-command'.
+          (dolist (file files)
+            (setq rsync-command
+                  (concat rsync-command
+                          (if (string-match "^/ssh:\\(.*\\)$" file)
+                              (format " -e ssh %s" (match-string 1 file))
+                            (shell-quote-argument file)) " ")))
+          ;; Append the destination directory to the `rsync-command'.
+          (setq rsync-command
+                (concat rsync-command
+                        (if (string-match "^/ssh:\\(.*\\)$" target)
+                            (format " -e ssh %s" (match-string 1 target))
+                          (shell-quote-argument target))))
+          ;; Run the async shell command.
+          (async-shell-command rsync-command)
+          ;; Finally, switch to that window.
+          (other-window 1)))))
+#+end_src
 * [[info:emacs#Package Installation][Install the selected packages (info)]]
 :PROPERTIES:
 :CUSTOM_ID: sec:install-selected-packages