[core] fix visual modes for narrow to indirect buffer

* Apply @duianto's fix to only activate visual selection it if it was active
  previous to the creation of the indirect buffer
* Block use of visual block mode because of continuing problems in that mode,
  and its questionable usefulness in this case
* Extract commonalities out of the narrowing functions
* Make the new keybindings into a list in the changelog for readability, per
  @duianto

CHANGELOG.develop

@@ -521,10 +521,12 @@ Other:
     terminal mode, but no longer in GUI mode. (emacs18)
 *** Core changes
 - Improvements:
-  - Provide keybindings for using narrow with an indirect buffer (to function
-    definition, ~SPC n F~; to page, ~SPC n P~; to region, ~SPC n R~) for when you
-    want narrowing multiple times in the same base buffer (thanks to Keith
-    Pinson and duianto)
+  - Provide keybindings for using narrow with an indirect buffer for when you
+    want narrowing multiple times in the same base buffer:
+    - ~SPC n F~ for narrow to function
+    - ~SPC n P~ for narrow to page
+    - ~SPC n R~ for narrow to region
+    (thanks to Keith Pinson and duianto)
   - Make =describe-text-properties= available in the help -> describe menu via
     ~SPC h d t~ (thanks to Keith Pinson)
   - Bind ~SPC c n~ to ~:cn~ / ~next-error~ and ~SPC c N~ to ~:cN~ / ~previous-error~

layers/+spacemacs/spacemacs-defaults/funcs.el

@@ -1728,26 +1728,36 @@ Decision is based on `dotspacemacs-line-numbers'."
 
 ;; narrow region
 
+(defun spacemacs/clone-indirect-buffer-de-activate-mark ()
+  "This is a workaround for the evil visual state error message like:
+Error in post-command-hook (evil-visual-post-command):
+(error \"Marker points into wrong buffer\" #<marker at 27875 in .spacemacs<2>>)"
+  (let ((region-was-active (region-active-p)))
+    (when region-was-active (deactivate-mark))
+    (call-interactively 'clone-indirect-buffer)
+    (when region-was-active (activate-mark))))
+
+(defun spacemacs/narrow-to-indirect-buffer (f x)
+  "Use the function `f' to narrow within an indirect buffer, except where the
+starting buffer is in a state (such as visual block mode) that would cause this
+to work incorrectly. `x' is the string name of the entity being narrowed to."
+  ;; There may be a way to get visual block mode working similar to the
+  ;; workaround we did for visual line mode; this usecase however seems like an
+  ;; edgecase at best, so let's patch it if we find out it's needed; otherwise
+  ;; let's not hold up the base functionality anymore.
+  (when (not (and (eq evil-state 'visual) (eq evil-visual-selection 'block)))
+    (spacemacs/clone-indirect-buffer-de-activate-mark)
+    (call-interactively f)
+    (message (format "%s narrowed to an indirect buffer" x))))
+
 (defun spacemacs/narrow-to-defun-indirect-buffer ()
   (interactive)
-  (deactivate-mark)
-  (call-interactively 'clone-indirect-buffer)
-  (activate-mark)
-  (call-interactively 'narrow-to-defun)
-  (message "Function narrowed to an indirect buffer"))
+  (spacemacs/narrow-to-indirect-buffer 'narrow-to-defun "Function"))
 
 (defun spacemacs/narrow-to-page-indirect-buffer ()
   (interactive)
-  (deactivate-mark)
-  (call-interactively 'clone-indirect-buffer)
-  (activate-mark)
-  (call-interactively 'narrow-to-page)
-  (message "Page narrowed to an indirect buffer"))
+  (spacemacs/narrow-to-indirect-buffer 'narrow-to-page "Page"))
 
 (defun spacemacs/narrow-to-region-indirect-buffer ()
   (interactive)
-  (deactivate-mark)
-  (call-interactively 'clone-indirect-buffer)
-  (activate-mark)
-  (call-interactively 'narrow-to-region)
-  (message "Region narrowed to an indirect buffer"))
+  (spacemacs/narrow-to-indirect-buffer 'narrow-to-region "Region"))