sync: Pass --allow-unrelated-histories to git merge when used with git git 2.9.0 or newer.

This makes merging a remote into a freshly created direct mode repository
work the same as it works in indirect mode.

The git-annex branches would get merged in any case by a sync,
since that doesn't use git merge.

This might need to be revisited later to better mirror git's behavior.

Assistant/Sync.hs

@@ -21,7 +21,6 @@ import Utility.Parallel
 import qualified Git
 import qualified Git.Command
 import qualified Git.Ref
-import qualified Git.Merge
 import qualified Remote
 import qualified Types.Remote as Remote
 import qualified Remote.List as Remote
@@ -239,19 +238,12 @@ manualPull currentbranch remotes = do
 			)
 	haddiverged <- liftAnnex Annex.Branch.forceUpdate
 	forM_ normalremotes $ \r ->
-		liftAnnex $ Command.Sync.mergeRemote r currentbranch mergeConfig
+		liftAnnex $ Command.Sync.mergeRemote r currentbranch Command.Sync.mergeConfig
 	u <- liftAnnex getUUID
 	forM_ xmppremotes $ \r ->
 		sendNetMessage $ Pushing (getXMPPClientID r) (PushRequest u)
 	return (catMaybes failed, haddiverged)
 
-mergeConfig :: [Git.Merge.MergeConfig]
-mergeConfig = 
-	[ Git.Merge.MergeNonInteractive
-	-- Pairing involves merging unrelated histories
-	, Git.Merge.MergeUnrelatedHistories
-	]
-
 {- Start syncing a remote, using a background thread. -}
 syncRemote :: Remote -> Assistant ()
 syncRemote remote = do

Assistant/Threads/Merger.hs

@@ -12,7 +12,6 @@ import Assistant.TransferQueue
 import Assistant.BranchChange
 import Assistant.DaemonStatus
 import Assistant.ScanRemotes
-import Assistant.Sync
 import Utility.DirWatcher
 import Utility.DirWatcher.Types
 import qualified Annex.Branch
@@ -86,7 +85,7 @@ onChange file
 					, "into", Git.fromRef b
 					]
 				void $ liftAnnex $ Command.Sync.merge
-					currbranch mergeConfig
+					currbranch Command.Sync.mergeConfig
 					Git.Branch.AutomaticCommit
 					changedbranch
 	mergecurrent _ = noop

CHANGELOG

@@ -6,6 +6,9 @@ git-annex (6.20161112) UNRELEASED; urgency=medium
     if so, either use stack to build, or run cabal with 
     --constraint='persistent ==2.2.4.1'
     Hopefully this mess with esqueleto will be resolved soon.
+  * sync: Pass --allow-unrelated-histories to git merge when used with git
+    git 2.9.0 or newer. This makes merging a remote into a freshly created
+    direct mode repository work the same as it works in indirect mode.
 
  -- Joey Hess <id@joeyh.name>  Tue, 15 Nov 2016 11:15:27 -0400
 

Command/Sync.hs

@@ -169,7 +169,12 @@ prepMerge :: Annex ()
 prepMerge = Annex.changeDirectory =<< fromRepo Git.repoPath
 
 mergeConfig :: [Git.Merge.MergeConfig]	
-mergeConfig = [Git.Merge.MergeNonInteractive]
+mergeConfig = 
+	[ Git.Merge.MergeNonInteractive
+	-- In several situations, unrelated histories should be merged
+	-- together. This includes pairing in the assistant etc.
+	, Git.Merge.MergeUnrelatedHistories
+	]
 
 merge :: CurrBranch -> [Git.Merge.MergeConfig] -> Git.Branch.CommitMode -> Git.Branch -> Annex Bool
 merge (Just b, Just adj) mergeconfig commitmode tomerge =