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.

3 files changed, 13 insertions, 8 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