Markdown reader: allow punctuation only internally in cite keys.

The characters '.',':',';','$','<','>','~','#','-','_' can
be used only between two letters or digits in a citation key.

This means that '@item1.' will be parsed as a citation, 'item1',
followed by a period, instead of a citation 'item1.', as was the
case previously.

Thanks to David Sanson for alerting us to the problem.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/Text/Pandoc/Readers/Markdown.hs b/src/Text/Pandoc/Readers/Markdown.hs
index 53531dc1a..f04ea88c4 100644
--- a/src/Text/Pandoc/Readers/Markdown.hs
+++ b/src/Text/Pandoc/Readers/Markdown.hs
@@ -1312,7 +1312,8 @@ citeKey = try $ do
   suppress_author <- option False (char '-' >> return True)
   char '@'
   first <- letter
-  rest <- many $ (noneOf ",;!?[]()@ \t\n")
+  let internal p = try $ p >>~ lookAhead (letter <|> digit)
+  rest <- many $ letter <|> digit <|> internal (oneOf ":.#$%&-_?<>~")
   let key = first:rest
   st <- getState
   guard $ key `elem` stateCitations st