add test case & fix conflict resolution bug on Windows & FAT

Fix bug in automatic merge conflict resolution code when used
on a filesystem not supporting symlinks, which resulted in it losing
track of the symlink bit of annexed files.

This was the underlying bug that was causing another test to fail,
which got worked around in 1c997fd08c.
I've chosen to keep 2 separate test cases since the old test case only
detected the problem accidentially.

Test suite passes on FAT & in windows, as well as on proper unix systems.

This commit was sponsored by Ellis Whitehead.

Test.hs

@@ -187,8 +187,8 @@ unitTests note getenv = testGroup ("Unit Tests " ++ note)
 	, check "sync" test_sync
 	, check "union merge regression" test_union_merge_regression
 	, check "conflict resolution" test_conflict_resolution_movein_bug
-	, check "sync push" test_sync_push
 	, check "conflict_resolution (mixed directory and file)" test_mixed_conflict_resolution
+	, check "conflict_resolution (mixed directory and file) 2" test_mixed_conflict_resolution2
 	, check "map" test_map
 	, check "uninit" test_uninit
 	, check "uninit (in git-annex branch)" test_uninit_inbranch
@@ -841,11 +841,19 @@ test_mixed_conflict_resolution env = do
 		any (variantprefix `isPrefixOf`) l
 			@? (what ++ " conflictor file missing in: " ++ show l )
 
-{- A windows-specific failure of mixed conflict resolution. -}
-test_sync_push :: TestEnv -> Assertion
-test_sync_push env = check >> check
+{- 
+ - During conflict resolution, one of the annexed files in git is
+ - accidentially converted from a symlink to a regular file.
+ - This only happens on crippled filesystems.
+ -
+ - This test case happens to detect the problem when it tries the next
+ - pass of conflict resolution, since it's unable to resolve a conflict
+ - between an annexed and non-annexed file.
+ -}
+test_mixed_conflict_resolution2 :: TestEnv -> Assertion
+test_mixed_conflict_resolution2 env = go >> go
   where
-	check = withtmpclonerepo env False $ \r1 ->
+	go = withtmpclonerepo env False $ \r1 ->
 		withtmpclonerepo env False $ \r2 -> do
 			indir env r1 $ do
 				writeFile conflictor "conflictor"