patch 8.0.0423: changing 'cinoptions' does not always work

Problem:    The effect of adding "#" to 'cinoptions' is not always removed.
            (David Briscoe)
Solution:   Reset b_ind_hash_comment. (Christian Brabandt, closes #1475)
diff --git a/src/testdir/test_cindent.vim b/src/testdir/test_cindent.vim
new file mode 100644
index 0000000..5685c2b
--- /dev/null
+++ b/src/testdir/test_cindent.vim
@@ -0,0 +1,16 @@
+" Test for cinoptions and cindent
+"
+" TODO: rewrite test3.in into this new style test
+
+func Test_cino_hash()
+  " Test that curbuf->b_ind_hash_comment is correctly reset
+  new
+  setlocal cindent cinoptions=#1
+  setlocal cinoptions=
+  call setline(1, ["#include <iostream>"])
+  call cursor(1, 1)
+  norm! o#include
+  "call feedkeys("o#include\<esc>", 't')
+  call assert_equal(["#include <iostream>", "#include"], getline(1,2))
+  bwipe!
+endfunc