better name for fallback sync refs

Don't expose these as branches in refs/heads/. Instead hide them away in
refs/synced/ where only show-ref will find them.

Make unused only look at branches and tags, not these other things,
so it won't care if some stale sync ref used to use a file.

This means they don't need to be deleted, which could have
led to an incoming sync being missed.

Assistant/Sync.hs

@@ -90,7 +90,7 @@ pushToRemotes threadname now st mpushmap remotes = do
 	go True branch g u remotes
 	where
 		go _ Nothing _ _ _ = return True -- no branch, so nothing to do
-		go shouldretry (Just branch) g u rs = do
+		go shouldretry (Just branch) g u rs =  do
 			debug threadname
 				[ "pushing to"
 				, show rs
@@ -133,12 +133,12 @@ pushToRemotes threadname now st mpushmap remotes = do
 			, Param $ refspec branch
 			] g
 			where
+				{- Push to refs/synced/uuid/branch; this
+				 - avoids cluttering up the branch display. -}
 				refspec b = concat
 					[ s
 					, ":"
-					, show $ Git.Ref.base $
-						Command.Sync.syncBranch $ Git.Ref $
-							"fallback" </> fromUUID u </> s
+					, "refs" </> "synced" </> fromUUID u </> s
 					]
 					where s = show $ Git.Ref.base b
 

Assistant/Threads/Merger.hs

@@ -15,18 +15,17 @@ import qualified Annex.Branch
 import qualified Git
 import qualified Git.Merge
 import qualified Git.Branch
-import qualified Git.Command as Git
 
 thisThread :: ThreadName
 thisThread = "Merger"
 
-{- This thread watches for changes to .git/refs/heads/synced/,
- - which indicate incoming pushes. It merges those pushes into the
- - currently checked out branch. -}
+{- This thread watches for changes to .git/refs/, looking for 
+ - incoming pushes. It merges those pushes into the currently
+ - checked out branch. -}
 mergeThread :: ThreadState -> NamedThread
 mergeThread st = thread $ do
 	g <- runThreadState st $ fromRepo id
-	let dir = Git.localGitDir g </> "refs" </> "heads" </> "synced"
+	let dir = Git.localGitDir g </> "refs"
 	createDirectoryIfMissing True dir
 	let hook a = Just $ runHandler g a
 	let hooks = mkWatchHooks
@@ -82,11 +81,6 @@ onAdd g file _
 					, show current
 					]
 				void $ Git.Merge.mergeNonInteractive changedbranch g
-				when ("fallback/" `isInfixOf` (show changedbranch)) $
-					void $ Git.runBool "branch"
-						[ Param "-D"
-						, Param $ show changedbranch
-						] g
 		go _ = noop
 
 equivBranches :: Git.Ref -> Git.Ref -> Bool
@@ -100,6 +94,6 @@ isAnnexBranch f = n `isSuffixOf` f
 		n = "/" ++ show Annex.Branch.name
 
 fileToBranch :: FilePath -> Git.Ref
-fileToBranch f = Git.Ref $ "refs" </> "heads" </> base
+fileToBranch f = Git.Ref $ "refs" </> base
 	where
-		base = Prelude.last $ split "/refs/heads/" f
+		base = Prelude.last $ split "/refs/" f

Command/Unused.hs

@@ -251,7 +251,9 @@ withKeysReferencedInGit a = do
 	rs <- relevantrefs <$> showref
 	forM_ rs (withKeysReferencedInGitRef a)
 	where
-		showref = inRepo $ Git.Command.pipeRead [Param "show-ref"]
+		{- List heads and tags, but not other refs used in syncing. -}
+		showref = inRepo $ Git.Command.pipeRead
+			[Param "show-ref", Param "--heads", Param "--tags"]
 		relevantrefs = map (Git.Ref .  snd) .
 			nubBy uniqref .
 			filter ourbranches .

Git/Ref.hs

@@ -49,9 +49,8 @@ sha branch repo = process <$> showref repo
 
 {- List of (refs, branches) matching a given ref spec. -}
 matching :: Ref -> Repo -> IO [(Ref, Branch)]
-matching ref repo = do
-	r <- pipeRead [Param "show-ref", Param $ show ref] repo
-	return $ map gen (lines r)
+matching ref repo = map gen . lines <$> 
+	pipeRead [Param "show-ref", Param $ show ref] repo
 	where
 		gen l = let (r, b) = separate (== ' ') l in
 			(Ref r, Ref b)