Allow disabling title exports or setting them to empty

.. because you can.

Now the org-export-with-title option is respected.

doc/ox-hugo-manual.org

@@ -323,15 +323,15 @@ The common =ox-hugo= export bindings are:
 
     A /valid Hugo post subtree/ is an Org subtree has the
  =EXPORT_FILE_NAME= property set.
-  - If the file is intended to be exported as a whole i.e. it must have
-    the #+TITLE keyword set, export the whole Org file a Hugo post in
-    Markdown.
+  - If the file is intended to be exported as a whole i.e. it must
+    have the =#+TITLE= keyword set, export the whole Org file a Hugo
+    post in Markdown.
 - =C-c C-e H A= :: Export *all* "What I Mean"
   - If the Org file has one or more 'valid Hugo post subtrees', export
     them to Hugo posts in Markdown.
   - If the file is intended to be exported as a whole (no 'valid Hugo
-    post subtrees' at all) i.e. it must have the #+TITLE keyword set,
-    export the whole Org file a Hugo post in Markdown.
+    post subtrees' at all) i.e. it must have the =#+TITLE= keyword
+    set, export the whole Org file a Hugo post in Markdown.
 **** For only the one-post-per-file flow
 - =C-c C-e H h= :: Export the Org file to a Hugo post in Markdown.
 *** Customization Options

ox-hugo.el

@@ -1671,15 +1671,20 @@ to ((name . \"foo\") (weight . 80))."
 - Remove bold, italics, monospace Markdown markup characters.
 - Do not escape underscore characters in the title.
 
+If exporting title is disabled by setting `org-export-with-title'
+to nil or using the OPTIONS keyword e.g. \"title:nil\", return
+nil.
+
 INFO is a plist used as a communication channel."
-  (let* ((title (org-export-data (plist-get info :title) info))
-         ;; Sanitize title.. cannot do bold, italics, monospace in title
-         (title (replace-regexp-in-string "\\\\?`" "" title))
-         (title (replace-regexp-in-string "\\`__?\\|\\`\\*\\*?\\|__?\\'\\|\\*\\*?\\'" "" title))
-         (title (replace-regexp-in-string " __?\\|__? \\| \\*\\*?\\|\\*\\*? " " " title))
-         ;; Do not escape underscores in title
-         (title (replace-regexp-in-string "\\\\_" "_" title)))
-    title))
+  (when (plist-get info :with-title)
+    (let* ((title (org-export-data (plist-get info :title) info))
+           ;; Sanitize title.. cannot do bold, italics, monospace in title
+           (title (replace-regexp-in-string "\\\\?`" "" title))
+           (title (replace-regexp-in-string "\\`__?\\|\\`\\*\\*?\\|__?\\'\\|\\*\\*?\\'" "" title))
+           (title (replace-regexp-in-string " __?\\|__? \\| \\*\\*?\\|\\*\\*? " " " title))
+           ;; Do not escape underscores in title
+           (title (replace-regexp-in-string "\\\\_" "_" title)))
+      title)))
 
 (defun org-hugo--transform-org-tags (tag-list info &optional no-prefer-hyphen)
   "Transform Org TAG-LIST for use in Hugo tags and categories.
@@ -2484,13 +2489,14 @@ approach)."
                       err msg)
                   (if valid-subtree-found
                       (setq msg "Point is not in a valid Hugo post subtree; move to one and try again")
-                    (let* ((info (org-export-get-environment 'hugo))
-                           (title (car (plist-get info :title))))
+                    (let ((title (save-excursion
+                                   (goto-char (point-min))
+                                   (re-search-forward "^#\\+TITLE:" nil :noerror))))
                       (if title
                           (setq do-export t)
                         (setq err t)
                         (setq msg (concat "The file neither contains a valid Hugo post subtree, "
-                                          "nor has the #+TITLE keyword set")))))
+                                          "nor has the #+TITLE keyword")))))
                   (unless do-export
                     (let ((error-fn (if (or (not err)
                                             noerror)

test/site/content-org/all-posts.org

@@ -292,7 +292,7 @@ in Markdown.
 Above title would render to ~Version 0.1 <span
 class="timestamp-wrapper"><span class="timestamp">&lt;2017-10-11
 Wed&gt;</span></span>~ in Markdown.
-* Title in Front Matter
+* Title in Front Matter                                               :title:
 ** Awesome title with "quoted text"
 :PROPERTIES:
 :EXPORT_FILE_NAME: post-title-quotes
@@ -306,6 +306,20 @@ Testing a post with double quotes in the title.
 :END:
 Ensure that the underscores in =title= string of front matter do not
 get escaped.. =foo_bar= must not become =foo\_bar=.
+** Allow empty titles                                                 :empty:
+:PROPERTIES:
+:EXPORT_FILE_NAME: allow-empty-titles-2
+:EXPORT_TITLE:
+:END:
+This post will be exported without =title= in the front-matter because
+it is explicitly set to /empty/ using =:EXPORT_TITLE:=.
+** Disable exporting title                                          :disable:
+:PROPERTIES:
+:EXPORT_OPTIONS: title:nil
+:EXPORT_FILE_NAME: disable-title-2
+:END:
+This post will be exported without =title= in the front-matter because
+it is disabled using =:EXPORT_OPTIONS: title:nil=.
 * Description meta-data with "quoted text"
 :PROPERTIES:
 :EXPORT_FILE_NAME: post-description-quotes

test/site/content-org/single-posts/allow-empty-titles-1.org

@@ -0,0 +1,15 @@
+#+HUGO_BASE_DIR: ../../
+
+#+TITLE:
+#+FILETAGS: empty title
+
+This post will be exported without =title= in the front-matter because
+it is explicitly set to /empty/ using =#+TITLE:=.
+
+* Footnotes
+* COMMENT Local Variables                                           :ARCHIVE:
+# Local Variables:
+# fill-column: 70
+# eval: (auto-fill-mode 1)
+# eval: (add-hook 'after-save-hook #'org-hugo-export-wim-to-md-after-save :append :local)
+# End:

test/site/content-org/single-posts/disable-title-1.org

@@ -0,0 +1,17 @@
+#+HUGO_BASE_DIR: ../../
+
+#+TITLE: Disable exporting title
+#+OPTIONS: title:nil
+
+#+FILETAGS: disable title
+
+This post will be exported without =title= in the front-matter because
+it is disabled using =#+OPTIONS: title:nil=.
+
+* Footnotes
+* COMMENT Local Variables                                           :ARCHIVE:
+# Local Variables:
+# fill-column: 70
+# eval: (auto-fill-mode 1)
+# eval: (add-hook 'after-save-hook #'org-hugo-export-wim-to-md-after-save :append :local)
+# End:

test/site/content/posts/allow-empty-titles-1.md

@@ -0,0 +1,6 @@
++++
+draft = false
++++
+
+This post will be exported without `title` in the front-matter because
+it is explicitly set to _empty_ using `#+TITLE:`.

test/site/content/posts/allow-empty-titles-2.md

@@ -0,0 +1,7 @@
++++
+tags = ["title", "empty"]
+draft = false
++++
+
+This post will be exported without `title` in the front-matter because
+it is explicitly set to _empty_ using `:EXPORT_TITLE:`.

test/site/content/posts/disable-title-1.md

@@ -0,0 +1,6 @@
++++
+draft = false
++++
+
+This post will be exported without `title` in the front-matter because
+it is disabled using `#+OPTIONS: title:nil`.

test/site/content/posts/disable-title-2.md

@@ -0,0 +1,7 @@
++++
+tags = ["title", "disable"]
+draft = false
++++
+
+This post will be exported without `title` in the front-matter because
+it is disabled using `:EXPORT_OPTIONS: title:nil`.

test/site/content/posts/post-title-quotes.md

@@ -1,6 +1,7 @@
 +++
 title = "Awesome title with \"quoted text\""
 date = 2017-07-24
+tags = ["title"]
 draft = false
 +++
 

test/site/content/posts/under-scores-in-title.md

@@ -1,6 +1,7 @@
 +++
 title = "Under_scores_in_title"
 date = 2017-07-28
+tags = ["title"]
 draft = false
 +++