+test_expect_success 'added submodule, set diff.submodule' "
+ git config diff.submodule log &&
+ git add sm1 &&
+ git diff --cached >actual &&
+ cat >expected <<-EOF &&
+Submodule sm1 0000000...$head1 (new submodule)
+EOF
+ git config --unset diff.submodule &&
+ test_cmp expected actual
+"
+
+test_expect_success '--submodule=short overrides diff.submodule' "
+ test_config diff.submodule log &&
+ git add sm1 &&
+ git diff --submodule=short --cached >actual &&
+ cat >expected <<-EOF &&
+diff --git a/sm1 b/sm1
+new file mode 160000
+index 0000000..a2c4dab
+--- /dev/null
++++ b/sm1
+@@ -0,0 +1 @@
++Subproject commit $fullhead1
+EOF
+ test_cmp expected actual
+"
+