Automatically detect changes in .spacemacs.template

core/core-dotspacemacs.el

@@ -49,6 +49,10 @@ then this is used. If ~/.spacemacs does not exist, then check
 for init.el in dotspacemacs-directory and use this if it
 exists. Otherwise, fallback to ~/.spacemacs")
 
+(defvar dotspacemacs-version nil
+  "Set in .spacemacs and used to check user's .spacemacs file
+format version against the .spacemacs template.")
+
 (defvar dotspacemacs-verbose-loading nil
   "If non nil output loading progess in `*Messages*' buffer.")
 
@@ -295,6 +299,56 @@ before copying the file if the destination already exists."
                          ".spacemacs.template") dotspacemacs-filepath t)
       (message "%s has been installed." dotspacemacs-filepath))))
 
+(defun dotspacemacs//file-hash (file)
+  "Get SHA1 hash of FILE."
+  (with-temp-buffer
+    (insert-file-contents-literally file)
+    (secure-hash 'sha1 (buffer-string))))
+
+(defun dotspacemacs/template-changed-p ()
+  "Compare hash of current template against cached template and
+return t if the template has changed. If there is a change (or no
+template has been chached yet) save new template value to cache
+file, meaning this function should only be called once on
+startup."
+  (let* ((cached-file
+          (expand-file-name (concat spacemacs-cache-directory
+                                    ".spacemacs.template")))
+         (old-hash
+          (when (file-exists-p cached-file)
+            (dotspacemacs//file-hash cached-file)))
+         (current-file
+          (expand-file-name (concat dotspacemacs-template-directory
+                                    ".spacemacs.template")))
+         (current-hash
+          (dotspacemacs//file-hash current-file))
+         (no-change? (and old-hash
+                          (string= old-hash current-hash))))
+    (unless no-change?
+      (copy-file current-file cached-file t))
+    (not no-change?)))
+
+(defun dotspacemacs//get-template-version ()
+  "Read the template version from .spacemacs.template"
+  (let (success)
+    (with-temp-buffer
+      (insert-file-contents
+       (concat dotspacemacs-template-directory ".spacemacs.template"))
+      (setq success
+            (re-search-forward
+             "^\\s-*?(setq\\s-+?dotspacemacs-version\\s-+?\"\\([0-9.]+\\)\"\\s-*?)"
+                     nil t))
+      (if success
+          (match-string 1)
+        (error "error: Cannot read .spacemacs.template version")))))
+
+(defun dotspacemacs/new-template-version-p ()
+  "Compare version of current template against user's .spacemacs
+version and return t if the template has changed."
+  (let ((dotspacemacs-template-version (dotspacemacs//get-template-version)))
+    (when dotspacemacs-version
+      (version< dotspacemacs-version dotspacemacs-template-version))))
+
 (defun dotspacemacs//ido-completing-read (prompt candidates)
   "Call `ido-completing-read' with a CANDIDATES alist where the key is
 a display strng and the value is the actual value to return."

core/core-spacemacs-buffer.el

@@ -27,6 +27,9 @@ version the release note it displayed")
 (defvar spacemacs-buffer--note-widgets nil
   "List of widgets used to display the release note.")
 
+(defvar spacemacs-buffer--dotfile-version-widget nil
+  "Widget displaying note about old dotfile version")
+
 (defvar spacemacs-buffer--previous-insert-type nil
   "Previous type of note inserted.")
 
@@ -63,6 +66,15 @@ Doge special text banner can be reachable via `999', `doge' or `random*'.
                                spacemacs-version)))
         (spacemacs-buffer/toggle-note (concat spacemacs-release-notes-directory "0.104.txt")
                                       'release-note))
+      ;; If the dotfile is installed first check for a change in the template
+      ;; version, then check for a change from the cached version
+      (when (file-exists-p dotspacemacs-filepath)
+        (if (dotspacemacs/new-template-version-p)
+            (spacemacs-buffer//insert-dotfile-template-note t)
+          ;; note the template changed function will always be nil if called a
+          ;; second time
+          (when (dotspacemacs/template-changed-p)
+            (spacemacs-buffer//insert-dotfile-template-note nil))))
       (spacemacs//redisplay))))
 
 (defun spacemacs-buffer//choose-banner ()
@@ -248,6 +260,28 @@ If TYPE is nil, just remove widgets."
   (spacemacs/dump-vars-to-file
    '(spacemacs-buffer--release-note-version) spacemacs-buffer--cache-file))
 
+(defun spacemacs-buffer//insert-dotfile-template-note (version-change?)
+  (let ((note (if version-change?
+                  "Your dotfile version is older than the version of the template "
+                "Detected change in dotfile template ")))
+    (widget-insert (concat "\n" note))
+    (setq spacemacs-buffer--dotfile-version-widget
+          (widget-create 'push-button
+                         :tag (propertize "Show diff with your dotfile" 'face 'font-lock-warning-face)
+                         :help-echo "Open ediff between your .spacemacs and template."
+                         :action (lambda (&rest ignore)
+                                   (spacemacs/ediff-dotfile-and-template)
+                                   (widget-delete spacemacs-buffer--dotfile-version-widget)
+                                   (with-current-buffer "*spacemacs*"
+                                     (let ((inhibit-read-only t))
+                                       (save-excursion
+                                         (goto-char (point-min))
+                                         (search-forward note nil t)
+                                         (replace-match "")))))
+                         :mouse-face 'highlight
+                         :follow-link "\C-m"))
+    (widget-insert "\n")))
+
 (defun spacemacs-buffer/set-mode-line (format)
   "Set mode-line format for spacemacs buffer."
   (with-current-buffer (get-buffer-create "*spacemacs*")

core/templates/.spacemacs.template

@@ -2,6 +2,11 @@
 ;; This file is loaded by Spacemacs at startup.
 ;; It must be stored in your home directory.
 
+;; Version of the .spacemacs file format. When the .spacemacs template is
+;; updated this version number will increase. If you comment out this line,
+;; the version check will be disabled.
+(setq dotspacemacs-version "0.0")
+
 (defun dotspacemacs/layers ()
   "Configuration Layers declaration.
 You should not put any user code in this function besides modifying the variable