emacs: Add support for deleting generations.

* doc/emacs.texi (emacs List buffer): Mention new key bindings.
* emacs/guix-base.el (guix-delete-generations): New procedure.
* emacs/guix-info.el (guix-generation-info-insert-number): Use it.
* emacs/guix-list.el (guix-generation-list-mark-delete,
  guix-generation-list-execute): New procedures.
* emacs/guix-main.scm (delete-generations*): New procedure.

doc/emacs.texi

@@ -105,8 +105,8 @@ many last generations.
 @end table
 
 By default commands for displaying packages display each output on a
-separate line.  If you prefer to see a list of packages (i.e.@: a list
-with a package per line), use the following setting:
+separate line.  If you prefer to see a list of packages---i.e., a list
+with a package per line, use the following setting:
 
 @example
 (setq guix-package-list-type 'package)
@@ -205,6 +205,11 @@ List packages installed in the current generation.
 @item i
 Describe marked generations (display available information in a
 ``generation-info'' buffer).
+@item d
+Mark the current generation for deletion (with prefix, mark all
+generations).
+@item x
+Execute actions on the marked generations---i.e., delete generations.
 @end table
 
 @node emacs Info buffer

emacs/guix-base.el

@@ -801,6 +801,20 @@ Return non-nil, if the operation should be continued; nil otherwise."
                  guix-operation-option-separator)))
   (force-mode-line-update))
 
+(defun guix-delete-generations (&rest generations)
+  "Delete GENERATIONS.
+Each element from GENERATIONS is a generation number."
+  (when (or (not guix-operation-confirm)
+              (y-or-n-p
+               (let ((count (length generations)))
+                 (if (> count 1)
+                     (format "Delete %d generations? " count)
+                   (format "Delete generation number %d? "
+                           (car generations))))))
+    (guix-eval-in-repl
+     (guix-make-guile-expression
+      'delete-generations* guix-current-profile generations))))
+
 (provide 'guix-base)
 
 ;;; guix-base.el ends here

emacs/guix-info.el

@@ -627,8 +627,10 @@ ENTRY is an alist with package info."
   (guix-info-insert-indent)
   (guix-info-insert-action-button
    "Delete"
-   (lambda (btn) (error "Sorry, not implemented yet"))
-   "Delete this generation"))
+   (lambda (btn)
+     (guix-delete-generations (button-get btn 'number)))
+   "Delete this generation"
+   'number number))
 
 (provide 'guix-info)
 

emacs/guix-list.el

@@ -728,8 +728,9 @@ Also see `guix-package-info-type'."
 
 (let ((map guix-generation-list-mode-map))
   (define-key map (kbd "RET") 'guix-generation-list-show-packages)
+  (define-key map (kbd "x")   'guix-generation-list-execute)
   (define-key map (kbd "i")   'guix-list-describe)
-  (define-key map (kbd "d")   'guix-generation-list-mark-delete-simple))
+  (define-key map (kbd "d")   'guix-generation-list-mark-delete))
 
 (defun guix-generation-list-show-packages ()
   "List installed packages for the generation at point."
@@ -737,6 +738,22 @@ Also see `guix-package-info-type'."
   (guix-get-show-entries 'list guix-package-list-type 'generation
                          (guix-list-current-id)))
 
+(defun guix-generation-list-mark-delete (&optional arg)
+  "Mark the current generation for deletion and move to the next line.
+With ARG, mark all generations for deletion."
+  (interactive "P")
+  (if arg
+      (guix-list-mark-all 'delete)
+    (guix-list-mark 'delete t)))
+
+(defun guix-generation-list-execute ()
+  "Delete marked generations."
+  (interactive)
+  (let ((marked (guix-list-get-marked-id-list 'delete)))
+    (or marked
+        (user-error "No generations marked for deletion"))
+    (apply #'guix-delete-generations marked)))
+
 (provide 'guix-list)
 
 ;;; guix-list.el ends here

emacs/guix-main.scm

@@ -815,3 +815,9 @@ OUTPUTS is a list of package outputs (may be an empty list)."
                                   "~a packages in profile~%"
                                   count)
                            count)))))))))
+
+(define (delete-generations* profile generations)
+  "Delete GENERATIONS from PROFILE.
+GENERATIONS is a list of generation numbers."
+  (with-store store
+    (delete-generations store profile generations)))