doc: new text-editor topic for cli

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

doc/cli/quick.md

@@ -21,5 +21,9 @@ keybindings are really useful to learn!
 | `help introduction` | An introduction to the CLI                 |
 | `help keybindings`  | Lists keybindings and other helpful tricks |
 | `help tutorial`     | The CLI User Guide                         |
+| `help text-editor`  | Help with the built-in text-editor command |
 
+> In `configure` context the `help setting` command shows the YANG
+> description text for each node and container.  To reach the admin
+> exec help from configure context, e.g., `do help text-editor`
 

doc/cli/text-editor.md

@@ -0,0 +1,70 @@
+# Text Editor
+
+The CLI built-in `text-editor` command can be used to edit type `binary`
+settings in configure context.
+
+The default editor is a Micro Emacs clone.  Users not familiar with
+terminal based editors may benefit from this introduction.
+
+
+## Escape Meta/Alt Control Shift
+
+When starting up, the editor status field at the bottom shows the
+following shorthand:
+
+```
+C-h q  quick help | C-h t  tutorial | C-h b  key bindings | C = Ctrl | M = Alt
+```
+
+Key combinations with a `-` (dash) mean holding down the modifier key.
+Combinations without a `-` (dash) mean without any modifier key.
+
+### Quick help `C-h q`
+
+  - hold down the `Ctrl` key on
+  - tap the `h` key
+  - release `Ctrl`
+  - tap the `q` key
+
+The bottom part of the terminal now shows a "buffer" called `*quick*`:
+
+```
+FILE              BUFFER           WINDOW            MARK/KILL        MISC
+C-x C-c exit      C-x b   switch   C-x 0 only other  C-space mark     C-_ undo
+C-x C-f find      C-x k   close    C-x 1 only this   C-w     kill-rg  C-s search
+C-x C-s save      C-x C-b list     C-x 2 split two   C-k     kill-ln  C-r r-search
+C-x s   save-all  C-x h   mark     C-x ^ enlarge     C-y     yank     M-% replace
+C-x i   insert    C-x g   goto-ln  C-x o other win   C-x C-x swap     M-q reformat
+```
+
+### Save & Exit `C-x C-c`
+
+  - Hold down the Ctrl key
+  - tap `X`
+  - tap `c`
+  - release `Ctrl`
+
+> The status field at the bottom asks if you are really sure, and/or if
+> you want to add a final Enter/newline to the file.  For binary content
+> that final newline may be important.
+
+
+## Changing the Editor
+
+The system has three different built-in editors: 
+
+ - `emacs` (Micro Emacs)
+ - `nano` (GNU Nano)
+ - `vi` (Visual Editor)
+
+Changing editor is done in configure context, in the system container:
+
+```
+admin@host:/> configure
+admin@host:/config/> edit system
+admin@host:/config/system/> set text-editor <TAB>
+emacs	nano	vi
+admin@host:/config/system/> set text-editor nano
+admin@host:/config/system/> leave
+admin@example:/> 
+```