test_cmp expect actual
'
+cat > expect << EOF
+diff --git a/HEAD b/HEAD
+new file mode 100644
+index 0000000..fe0cbee
+--- /dev/null
++++ b/HEAD
+@@ -0,0 +1 @@
++file-not-a-ref
+EOF
+
+test_expect_success 'stash where working directory contains "HEAD" file' '
+ git stash clear &&
+ git reset --hard &&
+ echo file-not-a-ref > HEAD &&
+ git add HEAD &&
+ test_tick &&
+ git stash &&
+ git diff-files --quiet &&
+ git diff-index --cached --quiet HEAD &&
+ test "$(git rev-parse stash^)" = "$(git rev-parse HEAD)" &&
+ git diff stash^..stash > output &&
+ test_cmp output expect
+'
+
test_done