refactored hook setup

Git/Hook.hs

@@ -0,0 +1,54 @@
+{- git hooks
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Git.Hook where
+
+import Common
+import Git
+import Utility.Tmp
+
+data Hook = Hook
+	{ hookName :: FilePath
+	, hookScript :: String
+	}
+
+hookFile :: Hook -> Repo -> FilePath
+hookFile h r = localGitDir r </> "hooks" </> hookName h
+
+{- Writes a hook. Returns False if the hook already exists with a different
+ - content. -}
+hookWrite :: Hook -> Repo -> IO Bool
+hookWrite h r = do
+	let f = hookFile h r
+	ifM (doesFileExist f)
+		( expectedContent h r
+		, do
+			viaTmp writeFile f (hookScript h)
+			p <- getPermissions f
+			setPermissions f $ p {executable = True}
+			return True
+		)
+
+{- Removes a hook. Returns False if the hook contained something else, and
+ - could not be removed. -}
+hookUnWrite :: Hook -> Repo -> IO Bool
+hookUnWrite h r = do
+	let f = hookFile h r
+	ifM (doesFileExist f)
+		( ifM (expectedContent h r)
+			( do
+				removeFile f
+				return True
+			, return False
+			)
+		, return True
+		)
+
+expectedContent :: Hook -> Repo -> IO Bool
+expectedContent h r = do
+	content <- readFile $ hookFile h r
+	return $ content == hookScript h