move commitStaged out of Command.Sync which no longer uses it

It's trivial enough that it it's not worth factoring it out to somewhere
in common with Command.Undo and the assistant.

Sponsored-by: the NIH-funded NICEMAN (ReproNim TR&D3) project

Assistant/Threads/Committer.hs

@@ -40,6 +40,7 @@ import qualified Database.Keys
 import qualified Command.Sync
 import qualified Command.Add
 import Config.GitConfig
+import qualified Git.Branch
 import Utility.Tuple
 import Utility.Metered
 import qualified Utility.RawFilePath as R
@@ -240,7 +241,11 @@ commitStaged msg = do
 		Left _ -> return False
 		Right _ -> do
 			cmode <- annexCommitMode <$> Annex.getGitConfig
-			ok <- Command.Sync.commitStaged cmode msg
+			ok <- inRepo $ Git.Branch.commitCommand cmode
+				(Git.Branch.CommitQuiet True)
+				[ Param "-m"
+				, Param msg
+				]
 			when ok $
 				Command.Sync.updateBranches =<< getCurrentBranch
 			return ok