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diff --git a/src/Hakyll/Core/Util/File.hs b/src/Hakyll/Core/Util/File.hs
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+++ b/src/Hakyll/Core/Util/File.hs
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+-- | A module containing various file utility functions
+--
+module Hakyll.Core.Util.File
+    ( makeDirectories
+    , getRecursiveContents
+    , isFileObsolete
+    ) where
+
+import System.FilePath (normalise, takeDirectory, (</>))
+import System.Time (ClockTime)
+import Control.Monad (forM)
+import System.Directory ( createDirectoryIfMissing, doesDirectoryExist
+                        , doesFileExist, getModificationTime
+                        , getDirectoryContents
+                        )
+
+-- | Given a path to a file, try to make the path writable by making
+--   all directories on the path.
+--
+makeDirectories :: FilePath -> IO ()
+makeDirectories = createDirectoryIfMissing True . takeDirectory
+
+-- | Get all contents of a directory. Note that files starting with a dot (.)
+--   will be ignored.
+--
+getRecursiveContents :: FilePath -> IO [FilePath]
+getRecursiveContents topdir = do
+    topdirExists <- doesDirectoryExist topdir
+    if topdirExists
+        then do names <- getDirectoryContents topdir
+                let properNames = filter isProper names
+                paths <- forM properNames $ \name -> do
+                    let path = topdir </> name
+                    isDirectory <- doesDirectoryExist path
+                    if isDirectory
+                        then getRecursiveContents path
+                        else return [normalise path]
+                return (concat paths)
+        else return []
+  where
+    isProper = not . (== ".") . take 1
+
+-- | Check if a timestamp is obsolete compared to the timestamps of a number of
+-- files. When they are no files, it is never obsolete.
+--
+isObsolete :: ClockTime    -- ^ The time to check.
+           -> [FilePath]   -- ^ Dependencies of the cached file.
+           -> IO Bool
+isObsolete _ [] = return False
+isObsolete timeStamp depends = do
+    dependsModified <- mapM getModificationTime depends
+    return (timeStamp < maximum dependsModified)
+
+-- | Check if a file is obsolete, given it's dependencies. When the file does
+-- not exist, it is always obsolete. Other wise, it is obsolete if any of it's
+-- dependencies has a more recent modification time than the file.
+--
+isFileObsolete :: FilePath    -- ^ The cached file
+               -> [FilePath]  -- ^ Dependencies of the cached file
+               -> IO Bool
+isFileObsolete file depends = do
+    exists <- doesFileExist file
+    if not exists
+        then return True
+        else do timeStamp <- getModificationTime file
+                isObsolete timeStamp depends