test/addSubmodule: try to fix integration

test/addSubmodule.vader

@@ -8,8 +8,8 @@ Execute (Stage untracked directory closed):
     call Cursor_position()
     call magit#stage_file()
     call Cd_test()
-    let diff=Git_diff('staged')
-    call Expect_diff(g:test_script_dir . 'addSubmodule/addSubmodule_diff.expect', diff)
+    let diff=Git_status(Get_filename())
+    call Expect_diff(g:test_script_dir . 'addSubmodule/addSubmodule_status.expect', diff)
     call Git_cmd("git reset")
 
 Execute (Stage untracked directory opened):
@@ -21,8 +21,8 @@ Execute (Stage untracked directory opened):
     call Cursor_position()
     call magit#stage_file()
     call Cd_test()
-    let diff=Git_diff('staged')
-    call Expect_diff(g:test_script_dir . 'addSubmodule/addSubmodule_diff.expect', diff)
+    let diff=Git_status(Get_filename())
+    call Expect_diff(g:test_script_dir . 'addSubmodule/addSubmodule_status.expect', diff)
     call Git_cmd("git reset")
 
 Include: cleanup.inc

test/addSubmodule/addSubmodule_diff.expect

-Submodule subdjooks a63bc77..6efcd49:
-  > books/models.py: first cover image support
-  > books/models.py: create Book entry with an isbn_search
-  > books/: add isbn_search module
-  > books/models.py: add BookManager
-  > migrations
-  > urls: add books urls in site urls
-  > views.py: fix typo
-  > urls: comment unsupported url

test/addSubmodule/addSubmodule_status.expect

+M  subdjooks

test/setup.inc

 Execute (setup):
   source $VIMAGIT_PATH/test/utils.vim
   call Cd_test()
-  call system("git reset --mixed " . $TEST_HEAD_SHA1 . "~1")
+  call system("git reset " . $TEST_HEAD_SHA1 . "~1")
   call Git_verbose_log(system("git status --porcelain"))
   call Cd_test_sub()