support git 2.34.0's handling of merge conflict between annexed and non-annexed file

This version of git -- or its new default "ort" resolver -- handles such
a conflict by staging two files, one with the original name and the other
named file~ref. Use unmergedSiblingFile when the latter is detected.

(It doesn't do that when the conflict is between a directory and a file
or symlink though, so see previous commit for how that case is handled.)

The sibling file has to be deleted separately, because cleanConflictCruft
may not delete it -- that only handles files that are annex links,
but the sibling file may be the non-annexed file side of the conflict.

The graftin code had assumed that, when the other side of a conclict
is a symlink, the file in the work tree will contain the non-annexed
content that we want it to contain. But that is not the case with the new
git; the file may be the annex link and needs to be replaced with the
content, while the annex link will be written as a -variant file.

(The weird doesDirectoryExist check in graftin turns out to still be
needed, test suite failed when I tried to remove it.)

Test suite passes with new git with ort resolver default. Have not tried it
with old git or other defaults.

Sponsored-by: Noam Kremen on Patreon

Git/LsFiles.hs

@@ -5,6 +5,8 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE OverloadedStrings #-}
+
 module Git.LsFiles (
 	Options(..),
 	inRepo,
@@ -236,7 +238,14 @@ data Unmerged = Unmerged
 	{ unmergedFile :: RawFilePath
 	, unmergedTreeItemType :: Conflicting TreeItemType
 	, unmergedSha :: Conflicting Sha
-	}
+	, unmergedSiblingFile :: Maybe RawFilePath
+	-- ^ Normally this is Nothing, because a
+	-- merge conflict is represented as a single file with two
+	-- stages. However, git resolvers sometimes choose to stage
+	-- two files, one for each side of the merge conflict. In such a case,
+	-- this is used for the name of the second file, which is related
+	-- to the first file. (Eg, "foo" and "foo~ref")
+	} deriving (Show)
 
 {- Returns a list of the files in the specified locations that have
  - unresolved merge conflicts.
@@ -246,7 +255,7 @@ data Unmerged = Unmerged
  -   1 = old version, can be ignored
  -   2 = us
  -   3 = them
- - If a line is omitted, that side removed the file.
+ - If line 2 or 3 is omitted, that side removed the file.
  -}
 unmerged :: [RawFilePath] -> Repo -> IO ([Unmerged], IO Bool)
 unmerged l repo = guardSafeForLsFiles repo $ do
@@ -265,7 +274,7 @@ data InternalUnmerged = InternalUnmerged
 	, ifile :: RawFilePath
 	, itreeitemtype :: Maybe TreeItemType
 	, isha :: Maybe Sha
-	}
+	} deriving (Show)
 
 parseUnmerged :: String -> Maybe InternalUnmerged
 parseUnmerged s
@@ -296,16 +305,25 @@ reduceUnmerged c (i:is) = reduceUnmerged (new:c) rest
 		{ unmergedFile = ifile i
 		, unmergedTreeItemType = Conflicting treeitemtypeA treeitemtypeB
 		, unmergedSha = Conflicting shaA shaB
+		, unmergedSiblingFile = if ifile sibi == ifile i
+			then Nothing
+			else Just (ifile sibi)
 		}
 	findsib templatei [] = ([], removed templatei)
 	findsib templatei (l:ls)
-		| ifile l == ifile templatei = (ls, l)
+		| ifile l == ifile templatei || issibfile templatei l = (ls, l)
 		| otherwise = (l:ls, removed templatei)
 	removed templatei = templatei
 		{ isus = not (isus templatei)
 		, itreeitemtype = Nothing
 		, isha = Nothing
 		}
+	-- foo~<ref> are unmerged sibling files of foo
+	-- Some versions or resolvers of git stage the sibling files,
+	-- other versions or resolvers do not.
+	issibfile x y = (ifile x <> "~") `S.isPrefixOf` ifile y
+		&& isus x || isus y
+		&& not (isus x && isus y)
 
 {- Gets the InodeCache equivilant information stored in the git index.
  -