t7512: test "detached from" as well

b397ea4 (status: show more info than "currently not on any
branch", 2013-03-13) wanted to make sure that after a checkout to
detach HEAD, the user can see where the HEAD was originally detached
from.  The last test added by that commit to t7512 shows one
example, immediately after HEAD is detached.  Enhance that test to
show "detached HEAD from" form that should be shown when the user
further resetted to another commit.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7512-status-help.sh

@@ -667,14 +667,22 @@ test_expect_success 'status when cherry-picking after resolving conflicts' '
 	test_i18ncmp expected actual
 '
 
-test_expect_success 'status showing detached from a tag' '
+test_expect_success 'status showing detached at and from a tag' '
 	test_commit atag tagging &&
 	git checkout atag &&
 	cat >expected <<-\EOF
 	# HEAD detached at atag
 	nothing to commit (use -u to show untracked files)
 	EOF
 	git status --untracked-files=no >actual &&
+	test_i18ncmp expected actual &&
+
+	git reset --hard HEAD^ &&
+	cat >expected <<-\EOF
+	# HEAD detached from atag
+	nothing to commit (use -u to show untracked files)
+	EOF
+	git status --untracked-files=no >actual &&
 	test_i18ncmp expected actual
 '