ox-texinfo: Fix escaping commas inside commands with multiple arguments

* lisp/ox-texinfo.el (org-texinfo--sanitize-content): Sanitize commas
everywhere to make sure that we do not end up with text commas being
interpreted as argument separator in @command{arg1, arg2, ...}.  This
approach will produce @comma{} even when it is not necessary, but it
is the safest approach.
(org-texinfo-plain-text): Update the comment.
* testing/lisp/test-ox-texinfo.el (test-ox-texinfo/escape-special-characters):
New test.

Reported-by: 8dcc <8dcc.git@gmail.com>
Link: https://orgmode.org/list/87set58skp.fsf@gmail.com

lisp/ox-texinfo.el

@@ -588,8 +588,11 @@ export state, as a plist."
 
 (defun org-texinfo--sanitize-content (text)
   "Escape special characters in string TEXT.
-Special characters are: @ { }"
-  (replace-regexp-in-string "[@{}]" "@\\&" text))
+Special characters are: @ { } ,"
+  (thread-last
+    text
+    (replace-regexp-in-string "[@{}]" "@\\&")
+    (replace-regexp-in-string "," "@comma{}")))
 
 (defun org-texinfo--wrap-float (value info &optional type label caption short)
   "Wrap string VALUE within a @float command.
@@ -1580,7 +1583,7 @@ contextual information."
   "Transcode a TEXT string from Org to Texinfo.
 TEXT is the string to transcode.  INFO is a plist holding
 contextual information."
-  ;; First protect @, { and }.
+  ;; First protect @, {, }, and commas (,).
   (let ((output (org-texinfo--sanitize-content text)))
     ;; Activate smart quotes.  Be sure to provide original TEXT string
     ;; since OUTPUT may have been modified.

testing/lisp/test-ox-texinfo.el

@@ -445,5 +445,26 @@ body
           (re-search-forward "Description")
           (re-search-forward "@end defvar")))))))
 
+
+;;; Escaping
+
+(ert-deftest test-ox-texinfo/escape-special-characters ()
+  "Test escaping special characters."
+  (should
+   (org-test-with-temp-text
+       (string-join
+        (list "[[https://example.com][Foo, Bar]]"
+              "[[https://example.com][Foo, Bar}]]")
+        "\n")
+     (let ((export-buffer "*Test Texinfo Export*")
+           (org-export-show-temporary-export-buffer nil))
+       (org-export-to-buffer 'texinfo export-buffer
+         nil nil nil nil nil
+         #'texinfo-mode)
+       (with-current-buffer export-buffer
+         (goto-char (point-min))
+         (should (search-forward "@uref{https://example.com, Foo@comma{} Bar}"))
+         (should (search-forward "@uref{https://example.com, Foo@comma{} Bar@}}")))))))
+
 (provide 'test-ox-texinfo)
 ;;; test-ox-texinfo.el end here