assistant: Deal with upcoming git's refusal to merge unrelated histories by default

git 2.8.1 (or perhaps 2.9.0) is going to prevent git merge from merging in
unrelated branches. Since the webapp's pairing etc features often combine
together repositories with unrelated histories, work around this behavior
change by setting GIT_MERGE_ALLOW_UNRELATED_HISTORIES when the assistant
merges.

Note though that this is not done for git annex sync's merges, so
it will follow git's default or configured behavior.

1 files changed, 17 insertions, 14 deletions

diff --git a/Command/Sync.hs b/Command/Sync.hs
index 5ec2f8bb3..3e68ad8cc 100644
--- a/Command/Sync.hs
+++ b/Command/Sync.hs
@@ -32,6 +32,7 @@ import Annex.Hook
 import qualified Git.Command
 import qualified Git.LsFiles as LsFiles
 import qualified Git.Branch
+import qualified Git.Merge
 import qualified Git.Types as Git
 import qualified Git.Ref
 import qualified Git
@@ -112,7 +113,7 @@ seek o = allowConcurrentOutput $ do
 	mapM_ includeCommandAction $ concat
 		[ [ commit o ]
 		, [ withbranch mergeLocal ]
-		, map (withbranch . pullRemote o) gitremotes
+		, map (withbranch . pullRemote o mergeconfig) gitremotes
 		,  [ mergeAnnex ]
 		]
 	when (contentOption o) $
@@ -123,13 +124,15 @@ seek o = allowConcurrentOutput $ do
 			-- and merge again to avoid our push overwriting
 			-- those changes.
 			mapM_ includeCommandAction $ concat
-				[ map (withbranch . pullRemote o) gitremotes
+				[ map (withbranch . pullRemote o mergeconfig) gitremotes
 				, [ commitAnnex, mergeAnnex ]
 				]
 	
 	void $ includeCommandAction $ withbranch pushLocal
 	-- Pushes to remotes can run concurrently.
 	mapM_ (commandAction . withbranch . pushRemote o) gitremotes
+  where
+	mergeconfig = [Git.Merge.MergeNonInteractive]
 
 type CurrBranch = (Maybe Git.Branch, Maybe Adjustment)
 
@@ -166,11 +169,11 @@ getCurrBranch = do
 prepMerge :: Annex ()
 prepMerge = Annex.changeDirectory =<< fromRepo Git.repoPath
 
-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 commitmode
+merge :: CurrBranch -> [Git.Merge.MergeConfig] -> Git.Branch.CommitMode -> Git.Branch -> Annex Bool
+merge (Just b, Just adj) mergeconfig commitmode tomerge =
+	updateAdjustedBranch tomerge (b, adj) mergeconfig commitmode
+merge (b, _) mergeconfig commitmode tomerge =
+	autoMergeFrom tomerge b mergeconfig commitmode
 
 syncBranch :: Git.Branch -> Git.Branch
 syncBranch = Git.Ref.under "refs/heads/synced" . fromDirectBranch . fromAdjustedBranch
@@ -257,7 +260,7 @@ mergeLocal currbranch@(Just branch, madj) = go =<< needmerge
 	go False = stop
 	go True = do
 		showStart "merge" $ Git.Ref.describe syncbranch
-		next $ next $ merge currbranch Git.Branch.ManualCommit syncbranch
+		next $ next $ merge currbranch [Git.Merge.MergeNonInteractive] Git.Branch.ManualCommit syncbranch
 	branch' = maybe branch (adjBranch . originalToAdjusted branch) madj
 mergeLocal (Nothing, _) = stop
 
@@ -291,13 +294,13 @@ updateBranch syncbranch updateto g =
 		, Param $ Git.fromRef $ updateto
 		] g
 
-pullRemote :: SyncOptions -> Remote -> CurrBranch -> CommandStart
-pullRemote o remote branch = stopUnless (pure $ pullOption o) $ do
+pullRemote :: SyncOptions -> [Git.Merge.MergeConfig] -> Remote -> CurrBranch -> CommandStart
+pullRemote o mergeconfig remote branch = stopUnless (pure $ pullOption o) $ do
 	showStart "pull" (Remote.name remote)
 	next $ do
 		showOutput
 		stopUnless fetch $
-			next $ mergeRemote remote branch
+			next $ mergeRemote remote branch mergeconfig
   where
 	fetch = inRepoWithSshOptionsTo (Remote.repo remote) (Remote.gitconfig remote) $
 		Git.Command.runBool
@@ -308,8 +311,8 @@ pullRemote o remote branch = stopUnless (pure $ pullOption o) $ do
  - were committed (or pushed changes, if this is a bare remote),
  - while the synced/master may have changes that some
  - other remote synced to this remote. So, merge them both. -}
-mergeRemote :: Remote -> CurrBranch -> CommandCleanup
-mergeRemote remote currbranch = ifM isBareRepo
+mergeRemote :: Remote -> CurrBranch -> [Git.Merge.MergeConfig] -> CommandCleanup
+mergeRemote remote currbranch mergeconfig = ifM isBareRepo
 	( return True
 	, case currbranch of
 		(Nothing, _) -> do
@@ -321,7 +324,7 @@ mergeRemote remote currbranch = ifM isBareRepo
 	)
   where
 	mergelisted getlist = and <$> 
-		(mapM (merge currbranch Git.Branch.ManualCommit . remoteBranch remote) =<< getlist)
+		(mapM (merge currbranch mergeconfig Git.Branch.ManualCommit . remoteBranch remote) =<< getlist)
 	tomerge = filterM (changed remote)
 	branchlist Nothing = []
 	branchlist (Just branch) = [branch, syncBranch branch]