Support git's core.sharedRepository configuration

This is incomplete, it does not honor it yet for hash directories
and other annex bookkeeping files. Some of that is not needed for a bare
repo; some of it may be.

Command/Unlock.hs

@@ -46,6 +46,6 @@ perform dest key = do
 			liftIO $ do
 				removeFile dest
 				moveFile tmpdest dest
-				allowWrite dest
+			thawContent dest
 			next $ return True
                 else error "copy failed!"