run out of tree merge with --no-ff

This is how direct mode does it too, and somehow, for reasons that
currently escape me, this makes git merge not care if it's run with an
empty work tree.

5 files changed, 20 insertions, 12 deletions

diff --git a/Annex/AdjustedBranch.hs b/Annex/AdjustedBranch.hs
index a30dda809..994444626 100644
--- a/Annex/AdjustedBranch.hs
+++ b/Annex/AdjustedBranch.hs
@@ -32,6 +32,7 @@ import qualified Git.Ref
 import qualified Git.Command
 import qualified Git.Tree
 import qualified Git.DiffTree
+import qualified Git.Merge
 import Git.Tree (TreeItem(..))
 import Git.Sha
 import Git.Env
@@ -272,13 +273,16 @@ updateAdjustedBranch tomerge (origbranch, adj) commitmode = catchBoolIO $
 			withemptydir tmpwt $ withWorkTree tmpwt $ do
 				liftIO $ writeFile (tmpgit </> "HEAD") (fromRef updatedorig)
 				showAction $ "Merging into " ++ fromRef (Git.Ref.base origbranch)
-				ifM (autoMergeFrom tomerge (Just origbranch) True commitmode)
-					( do
+				-- The --no-ff is important; it makes git
+				-- merge not care that the work tree is empty.
+				merged <- inRepo (Git.Merge.mergeNonInteractive' [Param "--no-ff"] tomerge commitmode)
+					<||> (resolveMerge (Just updatedorig) tomerge True <&&> commitResolvedMerge commitmode)
+				if merged
+					then do
 						!mergecommit <- liftIO $ extractSha <$> readFile (tmpgit </> "HEAD")
 						-- This is run after the commit lock is dropped.
 						return $ postmerge currbranch mergecommit
-					, return $ return False
-					)
+					else return $ return False
 	changestomerge Nothing _ = return $ return False
 	
 	withemptydir d a = bracketIO setup cleanup (const a)
@@ -305,7 +309,7 @@ updateAdjustedBranch tomerge (origbranch, adj) commitmode = catchBoolIO $
 		adjmergecommit <- commitAdjustedTree' adjtree mergecommit
 			[mergecommit, currbranch]
 		showAction "Merging into adjusted branch"
-		ifM (autoMergeFrom adjmergecommit (Just currbranch) False commitmode)
+		ifM (autoMergeFrom adjmergecommit (Just currbranch) commitmode)
 			-- The adjusted branch has a merge commit on top;
 			-- clean that up and propigate any changes made
 			-- in that merge to the origbranch.
diff --git a/Annex/AutoMerge.hs b/Annex/AutoMerge.hs
index e1662f81a..074e955d7 100644
--- a/Annex/AutoMerge.hs
+++ b/Annex/AutoMerge.hs
@@ -42,8 +42,8 @@ import qualified Data.ByteString.Lazy as L
  - Callers should use Git.Branch.changed first, to make sure that
  - there are changes from the current branch to the branch being merged in.
  -}
-autoMergeFrom :: Git.Ref -> Maybe Git.Ref -> Bool -> Git.Branch.CommitMode -> Annex Bool
-autoMergeFrom branch currbranch inoverlay commitmode = do
+autoMergeFrom :: Git.Ref -> Maybe Git.Ref -> Git.Branch.CommitMode -> Annex Bool
+autoMergeFrom branch currbranch commitmode = do
 	showOutput
 	case currbranch of
 		Nothing -> go Nothing
@@ -52,7 +52,7 @@ autoMergeFrom branch currbranch inoverlay commitmode = do
 	go old = ifM isDirect
 		( mergeDirect currbranch old branch (resolveMerge old branch False) commitmode
 		, inRepo (Git.Merge.mergeNonInteractive branch commitmode)
-			<||> (resolveMerge old branch inoverlay <&&> commitResolvedMerge commitmode)
+			<||> (resolveMerge old branch False <&&> commitResolvedMerge commitmode)
 		)
 
 {- Resolves a conflicted merge. It's important that any conflicts be
diff --git a/Annex/Direct.hs b/Annex/Direct.hs
index cd0835f04..782803e71 100644
--- a/Annex/Direct.hs
+++ b/Annex/Direct.hs
@@ -204,6 +204,7 @@ stageMerge d branch commitmode = do
 	-- has been updated, which would leave things in an inconsistent
 	-- state if mergeDirectCleanup is interrupted.
 	-- <http://marc.info/?l=git&m=140262402204212&w=2>
+	liftIO $ print ("stagemerge in", d)
 	merger <- ifM (coreSymlinks <$> Annex.getGitConfig)
 		( return Git.Merge.stageMerge
 		, return $ \ref -> Git.Merge.mergeNonInteractive ref commitmode
diff --git a/Command/Sync.hs b/Command/Sync.hs
index 9ef26f19e..69f39bb8a 100644
--- a/Command/Sync.hs
+++ b/Command/Sync.hs
@@ -170,7 +170,7 @@ merge :: CurrBranch -> Git.Branch.CommitMode -> Git.Branch -> Annex Bool
 merge (Just b, Just adj) commitmode tomerge =
 	updateAdjustedBranch tomerge (b, adj) commitmode
 merge (b, _) commitmode tomerge =
-	autoMergeFrom tomerge b False commitmode
+	autoMergeFrom tomerge b commitmode
 
 syncBranch :: Git.Branch -> Git.Branch
 syncBranch = Git.Ref.under "refs/heads/synced" . fromDirectBranch . fromAdjustedBranch
diff --git a/Git/Merge.hs b/Git/Merge.hs
index b3a048937..21eeaf181 100644
--- a/Git/Merge.hs
+++ b/Git/Merge.hs
@@ -15,12 +15,15 @@ import Git.Branch (CommitMode(..))
 
 {- Avoids recent git's interactive merge. -}
 mergeNonInteractive :: Ref -> CommitMode -> Repo -> IO Bool
-mergeNonInteractive branch commitmode
+mergeNonInteractive = mergeNonInteractive' []
+
+mergeNonInteractive' :: [CommandParam] -> Ref -> CommitMode -> Repo -> IO Bool
+mergeNonInteractive' extraparams branch commitmode
 	| older "1.7.7.6" = merge [Param $ fromRef branch]
 	| otherwise = merge $ [Param "--no-edit", Param $ fromRef branch]
   where
-	merge ps = runBool $ cp ++ [Param "merge"] ++ ps
-	cp
+	merge ps = runBool $ sp ++ [Param "merge"] ++ ps ++ extraparams
+	sp
 		| commitmode == AutomaticCommit =
 			[Param "-c", Param "commit.gpgsign=false"]
 		| otherwise = []