Add test for verbose commit cut line marker

Because:

* `git commit -v` uses the cut line marker to show the diff that would
  be commited at the bottom of the commit message. Anything after the
  cut line will not be included in the commit message.
* `git-good-commit` should therefore ignore these lines when validating
  the commit message.
* This functionality was added by
  #26 without a test.

Author: tommarshall

test/validation.bats

@@ -35,6 +35,20 @@ EOF
   assert_success
 }
 
+@test "validation: ignores lines after the verbose cut line" {
+  echo "n" > $FAKE_TTY
+  run git commit -m "$(cat <<EOF
+Add foo bar string to my_file
+
+# ------------------------ >8 ------------------------
+A line in the body that runs to longer than 72 characters after the verbose cut line
+EOF
+)"
+
+  assert_success
+}
+
+
 # 0. Good commits - control
 # ------------------------------------------------------------------------------