spacemacs-buffer: Distinguish types of updates

Add a spacemacs update button to the spacemacs buffer, and relabel the
package update button to read "Update Packages". This will hopefully
resolve some confusion about updating spacemacs vs. updating the
packages.

I also tweaked the switch-to-version function to make it a little more
verbose to use it for the spacemacs update button.

core/core-release-management.el

@@ -43,13 +43,21 @@ users on `develop' branch must manually pull last commits instead."
   (let ((branch (spacemacs/git-get-current-branch)))
     (if (string-equal "develop" branch)
         (message (concat "Cannot switch version because you are on develop.\n"
-                         "You have to manually `pull --rebase' last commits."))
-      (unless version (setq version (read-string "version: "
-                                                 (spacemacs/get-last-version))))
-      (when (or (string-equal "master" branch)
-                (yes-or-no-p (format (concat "You are not on master, are you "
-                                             "sure that you want to switch to "
-                                             "version %s ? ") version)))
+                         "You have to manually `pull --rebase' the latest commits."))
+      (unless version
+        (let ((last-version (spacemacs/get-last-version)))
+          (setq version (read-string
+                         (format "Version (default %s [latest]): " last-version)
+                         nil nil last-version))))
+      (when (and
+             (or (string-equal "master" branch)
+                 (yes-or-no-p (format (concat "You are not on master, are you "
+                                              "sure that you want to switch to "
+                                              "version %s ? ") version)))
+             (or (not (string-equal version spacemacs-version))
+                 (yes-or-no-p (format (concat "You are currently on the latest "
+                                              "version. This operation will "
+                                              "perform a hard reset. Continue? ")))))
         (let ((tag (concat "v" version)))
           (if (spacemacs/git-hard-reset-to-tag tag)
               (progn

core/core-spacemacs-buffer.el

@@ -444,19 +444,26 @@ HPADDING is the horizontal spacing betwee the content line and the frame border.
                  :follow-link "\C-m"
                  "https://gitter.im/syl20bnr/spacemacs")
   (insert " ")
+  (widget-create 'push-button
+                 :help-echo "Update Spacemacs core and layers."
+                 :action (lambda (&rest ignore) (spacemacs/switch-to-version))
+                 :mouse-face 'highlight
+                 :follow-link "\C-m"
+                 (propertize "Update Spacemacs" 'face 'font-lock-keyword-face))
+  (insert "\n               ")
   (widget-create 'push-button
                  :help-echo "Update all ELPA packages to the latest versions."
                  :action (lambda (&rest ignore) (configuration-layer/update-packages))
                  :mouse-face 'highlight
                  :follow-link "\C-m"
-                 (propertize "Update" 'face 'font-lock-keyword-face))
+                 (propertize "Update Packages" 'face 'font-lock-keyword-face))
   (insert " ")
   (widget-create 'push-button
-                 :help-echo "Rollback ELPA package upgrades if something got borked."
+                 :help-echo "Rollback ELPA package updates if something got borked."
                  :action (lambda (&rest ignore) (call-interactively 'configuration-layer/rollback))
                  :mouse-face 'highlight
                  :follow-link "\C-m"
-                 (propertize "Rollback" 'face 'font-lock-keyword-face))
+                 (propertize "Rollback Package Update" 'face 'font-lock-keyword-face))
   (insert "\n")
   (insert "                  ")
   (widget-create 'push-button

doc/DOCUMENTATION.org

@@ -9,6 +9,9 @@
  - [[#who-can-benefit-from-this][Who can benefit from this?]]
  - [[#update-and-rollback][Update and Rollback]]
    - [[#update-spacemacs-repository][Update Spacemacs repository]]
+      - [[#automatic-updates][Automatic Updates]]
+     - [[#updating-from-the-spacemacs-buffer][Updating from the Spacemacs Buffer]]
+     - [[#updating-manually-with-git][Updating Manually with git]]
    - [[#update-packages][Update packages]]
  - [[#configuration-layers][Configuration layers]]
    - [[#purpose][Purpose]]
@@ -277,30 +280,41 @@ one-page guide]] about how to learn Emacs.
 
 * Update and Rollback
 ** Update Spacemacs repository
+There are several methods of updating the core files and layer information for
+Spacemacs. It is recommended to update the packages first, see the next section.
+
+***  Automatic Updates
 Spacemacs will automatically check for a new version every startup. When it
 detects that a new version is available a arrow will appear in the modeline.
 Click it to update Spacemacs. You must restart Emacs after updating.
 
 Update Button:
 [[file:img/powerline-update.png]]
 
-*Note*: If you use the =develop= branch of Spacemacs, you must update manually.
+*Note*: If you use the =develop= branch of Spacemacs, you must update using git.
+
+*** Updating from the Spacemacs Buffer
+Use the button labeled "Update Spacemacs" in the Spacemacs buffer. You will be
+prompted for the version you would like to use. 
+
+*Note*: If you use the =develop= branch of Spacemacs, you cannot use this method.
+
+*** Updating Manually with git
 
 To update manually close Emacs and update the git repository:
 
 #+begin_src sh
   $ git pull --rebase
 #+end_src
 
-*Note*: It is recommended to update the packages first, see the next section.
 
 ** Update packages
-To update Spacemacs press RET (enter) or click on the link =[Update]= in the
-startup page under the banner then restart Emacs.
+To update the Emacs packages used by Spacemacs press RET (enter) or click on the
+link =[Update Packages]= in the startup page under the banner then restart Emacs.
 
-If anything goes wrong you should be able to rollback the update by pressing
-~RET~ or clicking on the =[Rollback]= link next to the =[Update]= link and
-choose a rollback slot (sorted by date).
+If anything goes wrong you should be able to rollback the update by pressing ~RET~
+or clicking on the =[Rollback Package Update]= link next to the =[Update Packages]=
+link and choose a rollback slot (sorted by date).
 
 * Configuration layers
 *Note*: This is a very simple overview of how layers work. A more extensive
@@ -1319,9 +1333,9 @@ The following helm actions are available on packages:
   - default: go the package init function
 
 **** New packages from ELPA repositories
-=package-list-packages= is where you can browse for all available packages in
-the different Elpa repositories. It is possible to upgrade packages from there
-but it is not recommended, use the =[Update]= link on the Spacemacs startup
+=package-list-packages= is where you can browse for all available packages in the
+different Elpa repositories. It is possible to upgrade packages from there but
+it is not recommended, use the =[Update Packages]= link on the Spacemacs startup
 page instead.
 
 Spacemacs uses [[https://github.com/Bruce-Connor/paradox][Paradox]] instead of =package-list-packages= to list available