unify handling of unusual GIT_INDEX_FILE relative path

This is probably a git bug that stuck in its interface.

Annex/GitOverlay.hs

@@ -19,10 +19,9 @@ import qualified Annex
 {- Runs an action using a different git index file. -}
 withIndexFile :: FilePath -> Annex a -> Annex a
 withIndexFile f a = do
-	-- Workaround http://thread.gmane.org/gmane.comp.version-control.git/294880
+	f' <- inRepo $ indexEnvVal f
-	absf <- liftIO $ absPath f
 	withAltRepo
-		(\g -> addGitEnv g indexEnv absf)
+		(\g -> addGitEnv g indexEnv f')
 		(\g g' -> g' { gitEnv = gitEnv g })
 		a
 

Git/Index.hs

@@ -9,11 +9,20 @@ module Git.Index where
 
 import Common
 import Git
+import Git.FilePath
 import Utility.Env
 
 indexEnv :: String
 indexEnv = "GIT_INDEX_FILE"
 
+{- When relative, GIT_INDEX_FILE is interpreted by git as being 
+ - relative to the top of the work tree of the git repository,
+ - not to the CWD. -}
+indexEnvVal :: FilePath -> Repo -> IO String
+indexEnvVal index r
+	| isAbsolute index = return index
+	| otherwise = getTopFilePath <$> toTopFilePath index r
+
 {- Forces git to use the specified index file.
  -
  - Returns an action that will reset back to the default
@@ -21,12 +30,11 @@ indexEnv = "GIT_INDEX_FILE"
  -
  - Warning: Not thread safe.
  -}
-override :: FilePath -> IO (IO ())
+override :: FilePath -> Repo -> IO (IO ())
-override index = do
+override index r = do
 	res <- getEnv var
-	-- Workaround http://thread.gmane.org/gmane.comp.version-control.git/294880
+	val <- indexEnvVal index r
-	absindex <- absPath index
+	setEnv var val True
-	setEnv var absindex True
 	return $ reset res
   where
 	var = "GIT_INDEX_FILE"

debian/changelog

@@ -15,7 +15,7 @@ git-annex (6.20160512) UNRELEASED; urgency=medium
     thing)
   * adjust: Add --fix adjustment, which is useful when the git directory
     is in a nonstandard place.
-  * Work around git bug in handling of relative path to GIT_INDEX_FILE
+  * Work around git weirdness in handling of relative path to GIT_INDEX_FILE
     when in a subdirectory of the repository. This affected git annex view.
   * Fix crash when entering/changing view in a subdirectory of a repo that
     has a dotfile in its root.

git-union-merge.hs

@@ -41,7 +41,7 @@ main :: IO ()
 main = do
 	[aref, bref, newref] <- map Git.Ref <$> parseArgs
 	g <- Git.Config.read =<< Git.CurrentRepo.get
-	_ <- Git.Index.override $ tmpIndex g
+	_ <- Git.Index.override (tmpIndex g) g
 	setup g
 	Git.UnionMerge.merge aref bref g
 	_ <- Git.Branch.commit Git.Branch.ManualCommit False "union merge" newref [aref, bref] g