feat: Add defcustom org-hugo-section-frag-property

This allows users to change the special property
`EXPORT_HUGO_SECTION*` to a string of their choice
e.g. `EXPORT_HUGO_SECTION_FRAG`.

Fixes #615.

ox-hugo.el

@@ -245,6 +245,12 @@ directory where all Hugo posts should go by default."
   :type 'directory)
 ;;;###autoload (put 'org-hugo-section 'safe-local-variable 'stringp)
 
+(defcustom org-hugo-section-frag-property "EXPORT_HUGO_SECTION*"
+  "Name of the property for Hugo section fragments."
+  :group 'org-export-hugo
+  :type 'string)
+;;;###autoload (put 'org-hugo-section-frag-property 'safe-local-variable 'stringp)
+
 (defcustom org-hugo-front-matter-format "toml"
   "Front-matter format.
 This variable can be set to either \"toml\" or \"yaml\"."
@@ -1563,9 +1569,11 @@ Search is case-insensitive."
   "Return the Hugo section path.
 This is the path relative to the Hugo \"content\" directory.
 
-If the EXPORT_HUGO_SECTION* keyword is set in the current or a
-parent subtree, return the concatenation of the \"HUGO_SECTION\"
-and the concatenated \"EXPORT_HUGO_SECTION*\" values as a path.
+If the property name from `org-hugo-section-frag-property'
+is set in the current or a parent subtree, return the
+concatenation of the \"HUGO_SECTION\" keyword and the
+concatenated values of `org-hugo-section-frag-property'
+property as a path.
 
 Else, return the \"HUGO_SECTION\" path.
 
@@ -1574,7 +1582,7 @@ The function always returns a string.
 INFO is a plist used as a communication channel."
   (let* ((hugo-section-prop (org-entry-get nil "EXPORT_HUGO_SECTION" :inherit))
          (hugo-section-kwd (plist-get info :hugo-section))
-         (hugo-section-frag-prop (org-entry-get nil "EXPORT_HUGO_SECTION*" :inherit))
+         (hugo-section-frag-prop (org-entry-get nil org-hugo-section-frag-property :inherit))
          (section-path-1 (or hugo-section-prop ;EXPORT_HUGO_SECTION gets higher precedence
                              hugo-section-kwd)) ;This is mainly to support per-file flow
          section-path)
@@ -1587,7 +1595,7 @@ INFO is a plist used as a communication channel."
     (when (org-string-nw-p hugo-section-frag-prop)
       (setq section-path-1
             (concat (file-name-as-directory section-path-1) ;Add trailing slash if absent
-                    (org-hugo--entry-get-concat nil "EXPORT_HUGO_SECTION*" "/"))))
+                    (org-hugo--entry-get-concat nil org-hugo-section-frag-property "/"))))
     (setq section-path (file-name-as-directory section-path-1))
     ;; (message "[ox-hugo section-path DBG] section path: %S" section-path)
     section-path))
@@ -2085,8 +2093,9 @@ Return nil if none of the above are true."
          (while (and pheading
                      (not (org-export-get-node-property :EXPORT_HUGO_SECTION pheading nil)))
            ;; Add the :EXPORT_HUGO_SECTION* value to the fragment list.
-           (when (setq fragment (org-export-get-node-property :EXPORT_HUGO_SECTION* pheading nil))
-             (push fragment fragments))
+           (let ((section-frag-prop-symbol (intern (format ":%s" org-hugo-section-frag-property))))
+             (when (setq fragment (org-export-get-node-property section-frag-prop-symbol pheading nil))
+               (push fragment fragments)))
            (setq pheading (org-element-property :parent pheading)))
 
          (when section
@@ -4260,7 +4269,6 @@ are \"toml\" and \"yaml\"."
                      "HUGO_ALLOW_SPACES_IN_TAGS"
                      "HUGO_BLACKFRIDAY"
                      "HUGO_SECTION"
-                     "HUGO_SECTION*"
                      "HUGO_BUNDLE"
                      "HUGO_BASE_DIR"
                      "HUGO_GOLDMARK"
@@ -4296,9 +4304,12 @@ are \"toml\" and \"yaml\"."
                      "HUGO_AUTO_SET_LASTMOD"
                      "LANGUAGE"
                      "AUTHOR")))
-    (mapcar (lambda (str)
-              (concat "EXPORT_" str))
-            prop-list)))
+    (setq prop-list
+          (mapcar (lambda (str)
+                    (concat "EXPORT_" str))
+                  prop-list))
+    (push org-hugo-section-frag-property prop-list)
+    prop-list))
 
 (defun org-hugo--get-valid-subtree ()
   "Return the Org element for a valid Hugo post subtree.