Improved bare autolink detection.

Previously we disallowed `-` at the end of an autolink,
and disallowed the combination `=-`.

This commit liberalizes the rules for allowing punctuation in
a bare URI.

Added test cases.

One potential drawback is that you can no longer put a bare
URI in em dashes like this

    this uri---http://example.com---is an example.

But in this respect we now match github's treatment of bare URIs.

Closes #2299.

src/Text/Pandoc/Parsing.hs

@@ -448,13 +448,12 @@ uri :: Stream [Char] m Char => ParserT [Char] st m (String, String)
 uri = try $ do
   scheme <- uriScheme
   char ':'
-  -- We allow punctuation except at the end, since
+  -- We allow sentence punctuation except at the end, since
   -- we don't want the trailing '.' in 'http://google.com.' We want to allow
   -- http://en.wikipedia.org/wiki/State_of_emergency_(disambiguation)
   -- as a URL, while NOT picking up the closing paren in
   -- (http://wikipedia.org). So we include balanced parens in the URL.
-  let isWordChar c = isAlphaNum c || c == '_' || c == '/' || c == '+' ||
-                         not (isAscii c)
+  let isWordChar c = isAlphaNum c || c `elem` "#$%*+/@\\_-"
   let wordChar = satisfy isWordChar
   let percentEscaped = try $ char '%' >> skipMany1 (satisfy isHexDigit)
   let entity = () <$ characterReference

tests/Tests/Readers/Markdown.hs

@@ -119,6 +119,10 @@ bareLinkTests =
       autolink "http://business.timesonline.co.uk/article/0,,9065-2473189,00.html")
   , ("http://www.mail-archive.com/ruby-talk@ruby-lang.org/",
       autolink "http://www.mail-archive.com/ruby-talk@ruby-lang.org/")
+  , ("https://example.org/?anchor=lala-",
+      autolink "https://example.org/?anchor=lala-")
+  , ("https://example.org/?anchor=-lala",
+      autolink "https://example.org/?anchor=-lala")
   ]
 
 {-