Added fix to allow dashes in pages.

Hakyll splits pages into metadata sections by lines starting
with `---`. Because of this, thing like

    Header
    ------

    Some text.

will not parse. This commit fixes this, by fixating the length
of the the dash pattern -- all dashed lines should contain the
same number of dashes. Therefor, you can use something like

    ---
    title: Foobar
    ---

    Header
    ------

    Some text.

3 files changed, 39 insertions, 11 deletions

diff --git a/hakyll.cabal b/hakyll.cabal
index ab53efd..6babb9d 100644
--- a/hakyll.cabal
+++ b/hakyll.cabal
@@ -1,5 +1,5 @@
 Name:               hakyll
-Version:            2.0
+Version:            2.1
 
 Synopsis:           A simple static site generator library.
 Description:        A simple static site generator library, mainly aimed at
diff --git a/src/Text/Hakyll/Internal/Page.hs b/src/Text/Hakyll/Internal/Page.hs
index 0ba8983..d3d0ec1 100644
--- a/src/Text/Hakyll/Internal/Page.hs
+++ b/src/Text/Hakyll/Internal/Page.hs
@@ -8,6 +8,7 @@ import Data.List (isPrefixOf)
 import Data.Char (isSpace)
 import Control.Monad.Reader (liftIO)
 import System.FilePath
+import Control.Monad.State (State, evalState, get, put)
 
 import Text.Pandoc
 
@@ -53,16 +54,25 @@ getRenderFunction fileType = writeHtmlString writerOptions
     readOptions _                       = readerOptions
 
 -- | Split a page into sections.
-splitAtDelimiters :: [String] -> [[String]]
-splitAtDelimiters [] = []
-splitAtDelimiters ls@(x:xs)
-    | isDelimiter x = let (content, rest) = break isDelimiter xs
-                      in (x : content) : splitAtDelimiters rest
-    | otherwise = [ls]
+splitAtDelimiters :: [String] -> State (Maybe String) [[String]]
+splitAtDelimiters [] = return []
+splitAtDelimiters ls@(x:xs) = do
+    delimiter <- get
+    if not (isDelimiter delimiter x)
+        then return [ls]
+        else do let proper = takeWhile (== '-') x
+                    (content, rest) = break (isDelimiter $ Just proper) xs
+                put $ Just proper
+                rest' <- splitAtDelimiters rest
+                return $ (x : content) : rest'
+  where
+    isDelimiter old = case old of
+        Nothing  -> isPossibleDelimiter
+        (Just d) -> (== d) . takeWhile (== '-')
 
 -- | Check if the given string is a metadata delimiter.
-isDelimiter :: String -> Bool
-isDelimiter = isPrefixOf "---"
+isPossibleDelimiter :: String -> Bool
+isPossibleDelimiter = isPrefixOf "---"
 
 -- | Read one section of a page.
 readSection :: (String -> String) -- ^ Render function.
@@ -76,7 +86,7 @@ readSection renderFunction isFirst ls
     | isFirst = readSimpleMetaData (tail ls)
     | otherwise = body (tail ls)
   where
-    isDelimiter' = isDelimiter (head ls)
+    isDelimiter' = isPossibleDelimiter (head ls)
     isNamedDelimiter = head ls `matchesRegex` "^----*  *[a-zA-Z0-9][a-zA-Z0-9]*"
     body ls' = [("body", renderFunction $ unlines ls')]
 
@@ -100,7 +110,7 @@ readPageFromFile path = do
     -- Read file.
     contents <- liftIO $ readFile path
     url <- toUrl path
-    let sections = splitAtDelimiters $ lines contents
+    let sections = evalState (splitAtDelimiters $ lines contents) Nothing
         sectionsData = concat $ zipWith ($) sectionFunctions sections
         context = M.fromList $
             ("url", url) : ("path", path) : category ++ sectionsData
diff --git a/tests/Page.hs b/tests/Page.hs
index ae1fcd9..1b80578 100644
--- a/tests/Page.hs
+++ b/tests/Page.hs
@@ -23,6 +23,7 @@ pageGroup = testGroup "Page"
     [ testCase "test_readPage_1" test_readPage_1
     , testCase "test_readPage_2" test_readPage_2
     , testCase "test_readPage_3" test_readPage_3
+    , testCase "test_readPage_4" test_readPage_4
     ]
 
 -- | An abstract function to test page reading.
@@ -68,3 +69,20 @@ test_readPage_3 = test_readPage fileName content assertion @? "test_readPage_3"
     content   = unlines [ "No metadata here, sorry."
                         ]
     assertion page =  M.lookup "body" page == Just "No metadata here, sorry.\n"
+
+-- | readPage test case 4.
+test_readPage_4 = test_readPage fileName content assertion @? "test_readPage_4"
+  where
+    fileName  = "test_readPage_4.txt"
+    content   = unlines [ "--- section"
+                        , "This is a section."
+                        , "---"
+                        , "Header"
+                        , "------"
+                        , "The header is not a separate section."
+                        ]
+    assertion page = M.lookup "body" page == Just body
+    body = unlines [ "Header"
+                   , "------"
+                   , "The header is not a separate section."
+                   ]