Allow auto-export on save to be enabled using .dir-locals.el

Works for either flow: per-subtree or per-file

Fixes #185.

.dir-locals.el

@@ -2,4 +2,6 @@
          (fill-column . 70)
          (sentence-end-double-space . t)))
  (org-mode . ((mode . auto-fill)))
- (markdown-mode . ((mode . auto-fill))))
+ (markdown-mode . ((mode . auto-fill)))
+ ("test/site/content-org"
+  . ((org-mode . ((org-hugo-auto-export-on-save . t))))))

ox-hugo-sugar.el

@@ -11,10 +11,27 @@
 
 ;;; Code:
 
+(defvar-local org-hugo-auto-export-on-save nil
+  "First enable flag for `org-hugo-export-wim-to-md-after-save'.
+
+This is a buffer local variable to enable auto-exporting using
+`ox-hugo' on file saving.  It is designed to be used in
+.dir-locals.el files.
+
+For example, put the below in your project's .dir-locals.el if
+the Org files in the \"content-org\" sub-directory are meant to
+be auto-exported using `ox-hugo':
+
+\((\"content-org\"
+  . ((org-mode . ((org-hugo-auto-export-on-save . t)))))) ")
+(put 'org-hugo-auto-export-on-save 'safe-local-variable 'booleanp)
+
 (defvar org-hugo-allow-export-after-save t
-  "Enable flag for `org-hugo-export-wim-to-md-after-save'.
-When nil, the above function will not export the Org file to
-Hugo-compatible Markdown.
+  "Second enable flag for `org-hugo-export-wim-to-md-after-save'.
+
+This variable is useful only if using Org Capture flow with
+per-subtree export flow.  See the ‘Auto-export on Saving’ section
+in this package's documentation for an example.
 
 This variable is usually set to nil by the user in
 `org-capture-before-finalize-hook' and set to t again in
@@ -25,19 +42,32 @@ Note that the export after save will not work until
 `org-hugo-export-wim-to-md-after-save' is added to the
 `after-save-hook' by the user.")
 
-;;;###autoload
 (defun org-hugo-export-wim-to-md-after-save ()
   "Fn for `after-save-hook' to run `org-hugo-export-wim-to-md'.
 
-The export is also skipped if `org-hugo-allow-export-after-save'
-is nil.  This variable is intended to be toggled dynamically in
-`org-capture-before-finalize-hook' and
+The export only if both and `org-hugo-auto-export-on-save' and
+`org-hugo-allow-export-after-save' are non-nil.
+
+`org-hugo-allow-export-after-save' is intended to be toggled
+dynamically in `org-capture-before-finalize-hook' and
 `org-capture-after-finalize-hook' hooks.  See the ‘Auto-export on
 Saving’ section in this package's documentation for an example."
   (save-excursion
-    (when org-hugo-allow-export-after-save
+    (when (and org-hugo-auto-export-on-save ;Should be set to t only in .dir-locals.el
+               ;; `org-hugo-allow-export-after-save' is t by default,
+               ;; and should be set to nil only temporarily, like
+               ;; during Org Capture.
+               org-hugo-allow-export-after-save)
       (org-hugo-export-wim-to-md))))
 
+(defun org-hugo-org-mode-hook-fn ()
+  "Hook function to enable/disable auto-export of Org file/subtree on file save.
+
+It is enabled if `org-hugo-auto-export-on-save' is non-nil."
+  (add-hook 'after-save-hook #'org-hugo-export-wim-to-md-after-save :append :local))
+
+(add-hook 'org-mode-hook #'org-hugo-org-mode-hook-fn)
+
 
 (provide 'ox-hugo-sugar)