post-recive hook to make updateInstead work in direct mode and adjusted branches

* Added post-recieve hook, which makes updateInstead work with direct
  mode and adjusted branches.
* init: Set up the post-receive hook.

This commit was sponsored by Fernando Jimenez on Patreon.

Git/ConfigTypes.hs

@@ -1,11 +1,11 @@
-{- git core.sharedRepository handling
+{- git config types
  -
- - Copyright 2012 Joey Hess <id@joeyh.name>
+ - Copyright 2012, 2017 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-module Git.SharedRepository where
+module Git.ConfigTypes where
 
 import Data.Char
 
@@ -14,6 +14,7 @@ import Git
 import qualified Git.Config
 
 data SharedRepository = UnShared | GroupShared | AllShared | UmaskShared Int
+	deriving (Eq)
 
 getSharedRepository :: Repo -> SharedRepository
 getSharedRepository r =
@@ -26,3 +27,14 @@ getSharedRepository r =
 		"world" -> AllShared
 		"everybody" -> AllShared
 		v -> maybe UnShared UmaskShared (readish v)
+
+data DenyCurrentBranch = UpdateInstead | RefusePush | WarnPush | IgnorePush
+	deriving (Eq)
+
+getDenyCurrentBranch :: Repo -> DenyCurrentBranch
+getDenyCurrentBranch r =
+	case map toLower $ Git.Config.get "receive.denycurrentbranch" "" r of
+		"updateinstead" -> UpdateInstead
+		"warn" -> WarnPush
+		"ignore" -> IgnorePush
+		_ -> RefusePush