Add some management functions to desktop list

This commit changes some of the interactive functions to first look if
the desktop list is being shown and, if so, if there is a desktop
specified under the cursor. If either of these conditions is not true,
they fall back to asking the user for a name, as before.

desktop-registry.el

@@ -49,10 +49,25 @@
 (defvar desktop-registry--history nil
   "History variable for `desktop-registry'.")
 
+(defvar desktop-registry-list-mode-map
+  (let ((map (make-sparse-keymap)))
+    (set-keymap-parent map tabulated-list-mode-map)
+    (define-key map "o" #'desktop-registry-change-desktop)
+    (define-key map "R" #'desktop-registry-rename-desktop)
+    (define-key map "d" #'desktop-registry-remove-desktop)
+    (define-key map "a" #'desktop-registry-add-directory)
+    (define-key map "A" #'desktop-registry-add-current-desktop)
+    map))
+
 (defun desktop-registry--canonicalize-dir (dir)
   "Canonicalize DIR for use."
   (directory-file-name (expand-file-name dir)))
 
+(defun desktop-registry--desktop-in-row ()
+  "If `desktop-registry-list-mode' is active, return the current rowid."
+  (and (eql major-mode 'desktop-registry-list-mode)
+       (tabulated-list-get-id)))
+
 ;;;###autoload
 (defun desktop-registry-current-desktop (&optional default)
   "Get the name of the currently loaded desktop.
@@ -107,10 +122,23 @@ current desktop as default value."
     (completing-read prompt desktop-registry-registry nil nil nil
                      'desktop-registry--history default)))
 
+(defun desktop-registry--get-desktop-name (&optional prompt
+                                                     default-current)
+  "Get the name of a desktop.
+
+This is done by either looking at the desktop name at point, in
+case `desktop-registry-list-mode' is active, or asks the user to
+provide a name with completion.  The parameters PROMPT and
+DEFAULT-CURRENT are passed directly to
+`desktop-registry--completing-read' when no desktop is found at
+point."
+  (or (desktop-registry--desktop-in-row)
+      (desktop-registry--completing-read prompt default-current)))
+
 ;;;###autoload
 (defun desktop-registry-remove-desktop (desktop)
   "Remove DESKTOP from the desktop registry."
-  (interactive (list (desktop-registry--completing-read "Remove: " t)))
+  (interactive (list (desktop-registry--get-desktop-name "Remove: " t)))
   (let ((spec (assoc desktop desktop-registry-registry)))
     (if spec
         (customize-save-variable
@@ -121,7 +149,7 @@ current desktop as default value."
 ;;;###autoload
 (defun desktop-registry-rename-desktop (old new)
   "Rename desktop OLD to NEW."
-  (interactive (list (desktop-registry--completing-read "Rename: " t)
+  (interactive (list (desktop-registry--get-desktop-name "Rename: " t)
                      (read-string "to: ")))
   (let ((spec (assoc old desktop-registry-registry)))
     (if (not spec)
@@ -133,7 +161,7 @@ current desktop as default value."
 ;;;###autoload
 (defun desktop-registry-change-desktop (name)
   "Change to the desktop named NAME."
-  (interactive (list (desktop-registry--completing-read "Switch to: ")))
+  (interactive (list (desktop-registry--get-desktop-name "Switch to: ")))
   (desktop-change-dir (cdr (assoc name desktop-registry-registry))))
 
 ;;;###autoload