Created attachment 1607 [details]
suggested patch

it may be a nit picking: EXPAND_MAX_KEYS, as any MAX macro, suggests that we can have up to EXPAND_MAX_KEYS keys. That's not true since if we reach the maximum, the following test bails out:

        if (num_keys >= EXPAND_MAX_KEYS)
                fatal("percent_expand: too many keys");

it's not a problem here since 16 becomes 15 which is still large enough but the issue is there anyway. I'm attaching a patch. In the patch changes, two "==" strings can be changed to ">=" if you feel it's better in terms of possible future updates. However, "==" is enough there.