Upgrading a direct mode repository to v6 has changed to enter an adjusted unlocked branch.

This makes the direct mode to v6 upgrade able to be performed in one clone
of a repository without affecting other clones, which can continue using v5
and direct mode.

Git/Branch.hs

@@ -184,21 +184,21 @@ commitTree commitmode message parentrefs tree repo =
 forcePush :: String -> String
 forcePush b = "+" ++ b
 
-{- Updates a branch (or other ref) to a new Sha. -}
-update :: String -> Branch -> Sha -> Repo -> IO ()
-update message branch sha = run
+{- Updates a branch (or other ref) to a new Sha or branch Ref. -}
+update :: String -> Branch -> Ref -> Repo -> IO ()
+update message branch r = run
 	[ Param "update-ref"
 	, Param "-m"
 	, Param message
 	, Param $ fromRef branch
-	, Param $ fromRef sha
+	, Param $ fromRef r
 	]
 
-update' :: Branch -> Sha -> Repo -> IO ()
-update' branch sha = run
+update' :: Branch -> Ref -> Repo -> IO ()
+update' branch r = run
 	[ Param "update-ref"
 	, Param $ fromRef branch
-	, Param $ fromRef sha
+	, Param $ fromRef r
 	]
 
 {- Checks out a branch, creating it if necessary. -}

Git/Ref.hs

@@ -18,6 +18,12 @@ import Data.Char (chr)
 headRef :: Ref
 headRef = Ref "HEAD"
 
+headFile :: Repo -> FilePath
+headFile r = localGitDir r </> "HEAD"
+
+setHeadRef :: Ref -> Repo -> IO ()
+setHeadRef ref r = writeFile (headFile r) ("ref: " ++ fromRef ref)
+
 {- Converts a fully qualified git ref into a user-visible string. -}
 describe :: Ref -> String
 describe = fromRef . base