core: Ask if unsaved changes in issue reports are about to be discarded

This prevents against working on an issue report and then accidentally killing
its buffer and losing everything just right before you are done....

core/core-debug.el

@@ -267,8 +267,17 @@ seconds to load")
           (goto-char (point-min))
           (search-forward placeholder)
           (replace-match replacement [keep-case] [literal])))
+    (set-buffer-modified-p nil)
     (spacemacs/report-issue-mode)))
 
+(defun spacemacs//report-issue-kill-buffer-query ()
+  "Check if issue has been edited when buffer is about to be
+  killed. Intended to be used with
+  `kill-buffer-query-functions'"
+  (if (buffer-modified-p)
+      (y-or-n-p "Issue has unsaved changes, kill buffer anyways? ")
+    t))
+
 (define-derived-mode spacemacs/report-issue-mode text-mode "Report-Issue"
   "Major mode for reporting issues with Spacemacs.
 
@@ -279,7 +288,10 @@ that the issue has been created successfully, you can close this buffer.
 \\{spacemacs/report-issue-mode-map}
 "
   (font-lock-add-keywords 'spacemacs/report-issue-mode
-                          '(("\\(<<.*?>>\\)" . 'font-lock-comment-face))))
+                          '(("\\(<<.*?>>\\)" . 'font-lock-comment-face)))
+  (add-hook 'kill-buffer-query-functions
+            'spacemacs//report-issue-kill-buffer-query
+            nil t))
 
 (define-key spacemacs/report-issue-mode-map
   (kbd "C-c C-c") 'spacemacs//report-issue-done)