better autostart file modification

As well as just being nicer, and less code, this uses nubBy equalFilePath
to ensure that the autostart file never gets dups.

Also, removing from the file no longer needs to be a perfect string match;
it also uses equalFilePath.

Config/Files.hs

@@ -24,26 +24,26 @@ autoStartFile = userConfigFile "autostart"
 readAutoStartFile :: IO [FilePath]
 readAutoStartFile = do
 	f <- autoStartFile
-	nub . lines <$> catchDefaultIO "" (readFile f)
+	nub . map dropTrailingPathSeparator . lines
+		<$> catchDefaultIO "" (readFile f)
+
+modifyAutoStartFile :: ([FilePath] -> [FilePath]) -> IO ()
+modifyAutoStartFile func = do
+	dirs <- readAutoStartFile
+	let dirs' = nubBy equalFilePath $ func dirs
+	when (dirs' /= dirs) $ do
+		f <- autoStartFile
+		createDirectoryIfMissing True (parentDir f)
+		viaTmp writeFile f $ unlines $ dirs'
 
 {- Adds a directory to the autostart file. -}
 addAutoStartFile :: FilePath -> IO ()
-addAutoStartFile path = do
-	dirs <- readAutoStartFile
-	when (path `notElem` dirs) $ do
-		f <- autoStartFile
-		createDirectoryIfMissing True (parentDir f)
-		viaTmp writeFile f $ unlines $ dirs ++ [path]
+addAutoStartFile path = modifyAutoStartFile $ (:) path
 
 {- Removes a directory from the autostart file. -}
 removeAutoStartFile :: FilePath -> IO ()
-removeAutoStartFile path = do
-	dirs <- readAutoStartFile
-	when (path `elem` dirs) $ do
-		f <- autoStartFile
-		createDirectoryIfMissing True (parentDir f)
-		viaTmp writeFile f $ unlines $
-			filter (not . equalFilePath path) dirs
+removeAutoStartFile path = modifyAutoStartFile $
+	filter (not . equalFilePath path)
 
 {- The path to git-annex is written here; which is useful when cabal
  - has installed it to some aweful non-PATH location. -}