+test_expect_success 'will not overwrite untracked subtree' '
+ git reset --hard c0 &&
+ rm -rf sub &&
+ mkdir -p sub/f &&
+ cp important sub/f/important &&
+ test_must_fail git merge sub &&
+ test_path_is_missing .git/MERGE_HEAD &&
+ test_cmp important sub/f/important
+'
+
+test_expect_failure 'will not overwrite untracked file in leading path' '
+ git reset --hard c0 &&
+ rm -rf sub &&
+ cp important sub &&
+ test_must_fail git merge sub &&
+ test_path_is_missing .git/MERGE_HEAD &&
+ test_cmp important sub
+'
+
+test_expect_failure SYMLINKS 'will not overwrite untracked symlink in leading path' '
+ git reset --hard c0 &&
+ rm -rf sub &&
+ mkdir sub2 &&
+ ln -s sub2 sub &&
+ test_must_fail git merge sub &&
+ test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success SYMLINKS 'will not be confused by symlink in leading path' '
+ git reset --hard c0 &&
+ rm -rf sub &&
+ ln -s sub2 sub &&
+ git add sub &&
+ git commit -m ln &&
+ git checkout sub
+'
+