revert parentDir change

Reverts 965e106f24

Unfortunately, this caused breakage on Windows, and possibly elsewhere,
because parentDir and takeDirectory do not behave the same when there is a
trailing directory separator.

Utility/Daemon.hs

@@ -83,7 +83,7 @@ foreground pidfile a = do
  - Fails if the pid file is already locked by another process. -}
 lockPidFile :: FilePath -> IO ()
 lockPidFile pidfile = do
-	createDirectoryIfMissing True (takeDirectory pidfile)
+	createDirectoryIfMissing True (parentDir pidfile)
 #ifndef mingw32_HOST_OS
 	fd <- openFd pidfile ReadWrite (Just stdFileMode) defaultFileFlags
 	locked <- catchMaybeIO $ setLock fd (WriteLock, AbsoluteSeek, 0, 0)
@@ -176,6 +176,6 @@ winLockFile pid pidfile = do
 	prefix = pidfile ++ "."
 	suffix = ".lck"
 	cleanstale = mapM_ (void . tryIO . removeFile) =<<
-		(filter iswinlockfile <$> dirContents (takeDirectory pidfile))
+		(filter iswinlockfile <$> dirContents (parentDir pidfile))
 	iswinlockfile f = suffix `isSuffixOf` f && prefix `isPrefixOf` f
 #endif

Utility/FreeDesktop.hs

@@ -27,6 +27,7 @@ module Utility.FreeDesktop (
 ) where
 
 import Utility.Exception
+import Utility.Path
 import Utility.UserInfo
 import Utility.Process
 import Utility.PartialPrelude
@@ -78,7 +79,7 @@ buildDesktopMenuFile d = unlines ("[Desktop Entry]" : map keyvalue d) ++ "\n"
 
 writeDesktopMenuFile :: DesktopEntry -> String -> IO ()
 writeDesktopMenuFile d file = do
-	createDirectoryIfMissing True (takeDirectory file)
+	createDirectoryIfMissing True (parentDir file)
 	writeFile file $ buildDesktopMenuFile d
 
 {- Path to use for a desktop menu file, in either the systemDataDir or

Utility/LinuxMkLibs.hs

@@ -29,13 +29,13 @@ installLib installfile top lib = ifM (doesFileExist lib)
 	( do
 		installfile top lib
 		checksymlink lib
-		return $ Just $ takeDirectory lib
+		return $ Just $ parentDir lib
 	, return Nothing
 	)
   where
 	checksymlink f = whenM (isSymbolicLink <$> getSymbolicLinkStatus (inTop top f)) $ do
 		l <- readSymbolicLink (inTop top f)
-		let absl = absPathFrom (takeDirectory f) l
+		let absl = absPathFrom (parentDir f) l
 		target <- relPathDirToFile (takeDirectory f) absl
 		installfile top absl
 		nukeFile (top ++ f)

Utility/Path.hs

@@ -77,12 +77,18 @@ absNormPathUnix dir path = todos <$> MissingH.absNormPath (fromdos dir) (fromdos
 	todos = replace "/" "\\"
 #endif
 
-{- Just the parent directory of a path, or Nothing if the path has no
- - parent (ie for "/") -}
-parentDir :: FilePath -> Maybe FilePath
+{- Returns the parent directory of a path.
+ -
+ - To allow this to be easily used in loops, which terminate upon reaching the
+ - top, the parent of / is ""
+ -
+ - An additional subtle difference between this and takeDirectory
+ - is that takeDirectory "foo/bar/" is "foo/bar", while parentDir is "foo"
+ -}
+parentDir :: FilePath -> FilePath
 parentDir dir
-	| null dirs = Nothing
-	| otherwise = Just $ joinDrive drive (join s $ init dirs)
+	| null dirs = ""
+	| otherwise = joinDrive drive (join s $ init dirs)
   where
 	-- on Unix, the drive will be "/" when the dir is absolute, otherwise ""
 	(drive, path) = splitDrive dir
@@ -92,8 +98,8 @@ parentDir dir
 prop_parentDir_basics :: FilePath -> Bool
 prop_parentDir_basics dir
 	| null dir = True
-	| dir == "/" = parentDir dir == Nothing
-	| otherwise = p /= Just dir
+	| dir == "/" = parentDir dir == ""
+	| otherwise = p /= dir
   where
 	p = parentDir dir