git annex add in adjusted unlocked branch

Cached the current branch lookup just because it seems unnecessary overhead
to run an extra git command per add to query the current branch.

Annex.hs

@@ -136,6 +136,7 @@ data AnnexState = AnnexState
 	, workers :: [Either AnnexState (Async AnnexState)]
 	, concurrentjobs :: Maybe Int
 	, keysdbhandle :: Maybe Keys.DbHandle
+	, cachedcurrentbranch :: Maybe Git.Branch
 	}
 
 newState :: GitConfig -> Git.Repo -> AnnexState
@@ -182,6 +183,7 @@ newState c r = AnnexState
 	, workers = []
 	, concurrentjobs = Nothing
 	, keysdbhandle = Nothing
+	, cachedcurrentbranch = Nothing
 	}
 
 {- Makes an Annex state object for the specified git repo.