org-link-plain-re: Improve heuristic regexp for plain link detection

* lisp/ol.el (org-link-make-regexps): Allow trailing ?- at the end of
the plain links.
* etc/ORG-NEWS (Trailing =-= is now allowed in plain links): Announce
the change.

Link: https://orgmode.org/list/87sexh9ddv.fsf@ice9.digital

etc/ORG-NEWS

@@ -60,6 +60,23 @@ all the references are resolved in the generated png.
 # This also includes changes in function behavior from Elisp perspective.
 
 ** Miscellaneous
+*** Trailing =-= is now allowed in plain links
+
+Previously, plain links like
+
+: https://domain/test-
+
+did not include the trailing =-= punctuation.
+
+Now, the =-= is allowed at the end, and is considered a part of the plain link.
+
+#+begin_quote
+These types of links will likely be encountered for sites where anchor
+targets are automatically generated from documentation headings which
+are questions.
+         https://list.orgmode.org/orgmode/87sexh9ddv.fsf@ice9.digital/
+#+end_quote
+
 *** =org-attach= now considers symlinked files when searching pre-existing attach dirs
 
 When Org buffer is opened from a symlink, Org mode looks into the

lisp/ol.el

@@ -944,6 +944,12 @@ This should be called after the variable `org-link-parameters' has changed."
 		    (1+ (or (regex ,non-space-bracket)
 			    ,parenthesis))
 		    (or (regexp "[^[:punct:] \t\n]")
+                        ;; Allow "-" punctuation, as an exception
+                        ;; See https://list.orgmode.org/orgmode/87sexh9ddv.fsf@ice9.digital/
+                        ;; This is also in line with the heuristics
+                        ;; above - it also does not include "-"
+                        ;; punctuation.
+                        ?-
 		        ?/
 		        ,parenthesis)))))
           org-link-bracket-re