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, 34 insertions, 13 deletions

diff --git a/Git/Merge.hs b/Git/Merge.hs
index 21eeaf181..c783521df 100644
--- a/Git/Merge.hs
+++ b/Git/Merge.hs
@@ -1,36 +1,51 @@
 {- git merging
  -
- - Copyright 2012, 2014 Joey Hess <id@joeyh.name>
+ - Copyright 2012-2016 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-module Git.Merge where
+module Git.Merge (
+	MergeConfig(..),
+	CommitMode(..),
+	merge,
+	merge',
+	stageMerge,
+) where
 
 import Common
 import Git
 import Git.Command
 import Git.BuildVersion
 import Git.Branch (CommitMode(..))
+import Git.Env
 
-{- Avoids recent git's interactive merge. -}
-mergeNonInteractive :: Ref -> CommitMode -> Repo -> IO Bool
-mergeNonInteractive = mergeNonInteractive' []
+data MergeConfig
+	= MergeNonInteractive
+	-- ^ avoids recent git's interactive merge
+	| MergeUnrelatedHistories
+	-- ^ avoids recent git's prevention of merging unrelated histories
+	deriving (Eq)
 
-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]
+merge :: Ref -> [MergeConfig] -> CommitMode -> Repo -> IO Bool
+merge = merge' []
+
+merge' :: [CommandParam] -> Ref -> [MergeConfig] -> CommitMode -> Repo -> IO Bool
+merge' extraparams branch mergeconfig commitmode r
+	| MergeNonInteractive `notElem` mergeconfig || older "1.7.7.6" =
+		go [Param $ fromRef branch]
+	| otherwise = go [Param "--no-edit", Param $ fromRef branch]
   where
-	merge ps = runBool $ sp ++ [Param "merge"] ++ ps ++ extraparams
+	go ps = runBool (sp ++ [Param "merge"] ++ ps ++ extraparams)
+		=<< cfgRepo mergeconfig r
 	sp
 		| commitmode == AutomaticCommit =
 			[Param "-c", Param "commit.gpgsign=false"]
 		| otherwise = []
 
 {- Stage the merge into the index, but do not commit it.-}
-stageMerge :: Ref -> Repo -> IO Bool
-stageMerge branch = runBool
+stageMerge :: Ref -> [MergeConfig] -> Repo -> IO Bool
+stageMerge branch mergeconfig r = runBool
 	[ Param "merge"
 	, Param "--quiet"
 	, Param "--no-commit"
@@ -38,4 +53,10 @@ stageMerge branch = runBool
 	-- commit.
 	, Param "--no-ff"
 	, Param $ fromRef branch
-	]
+	] =<< cfgRepo mergeconfig r
+
+cfgRepo :: [MergeConfig] -> Repo -> IO Repo
+cfgRepo mergeconfig r
+	| MergeUnrelatedHistories `elem` mergeconfig =
+		addGitEnv r "GIT_MERGE_ALLOW_UNRELATED_HISTORIES" "1"
+	| otherwise = return r