RST reader: Handle chained link definitions.

For example,

    .. _hello:
    .. _goodbye: example.com

Here both `hello` and `goodbye` should link to `example.com`.

Fixes the first part of #262.

src/Text/Pandoc/Readers/RST.hs

@@ -31,7 +31,7 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 Conversion from reStructuredText to 'Pandoc' document.
 -}
 module Text.Pandoc.Readers.RST ( readRST ) where
-import Control.Monad (guard, liftM, mzero, when)
+import Control.Monad (guard, liftM, mzero, when, forM_)
 import Control.Monad.Identity (Identity(..))
 import Control.Monad.Except (throwError)
 import Data.Char (isHexDigit, isSpace, toLower, toUpper)
@@ -1054,16 +1054,29 @@ stripTicks = reverse . stripTick . reverse . stripTick
   where stripTick ('`':xs) = xs
         stripTick xs       = xs
 
+referenceNames :: PandocMonad m => RSTParser m [String]
+referenceNames = do
+  let rn = try $ do
+             string ".. _"
+             (_, ref) <- withRaw referenceName
+             char ':'
+             return ref
+  first <- rn
+  rest  <- many (try (blanklines *> rn))
+  return (first:rest)
+
 regularKey :: PandocMonad m => RSTParser m ()
 regularKey = try $ do
-  string ".. _"
-  (_,ref) <- withRaw referenceName
-  char ':'
+  -- we allow several references to the same URL, e.g.
+  -- .. _hello:
+  -- .. _goodbye: url.com
+  refs <- referenceNames
   src <- targetURI
-  let key = toKey $ stripTicks ref
   --TODO: parse width, height, class and name attributes
-  updateState $ \s -> s { stateKeys = M.insert key ((src,""), nullAttr) $
-                          stateKeys s }
+  let keys = map (toKey . stripTicks) refs
+  forM_ keys $ \key ->
+    updateState $ \s -> s { stateKeys = M.insert key ((src,""), nullAttr) $
+                            stateKeys s }
 
 headerBlock :: PandocMonad m => RSTParser m [Char]
 headerBlock = do

test/command/262.md

@@ -0,0 +1,9 @@
+```
+% pandoc -f rst
+`hello`_ and `goodbye`_
+
+.. _hello:
+.. _goodbye: example.com
+^D
+<p><a href="example.com">hello</a> and <a href="example.com">goodbye</a></p>
+```