Refreshing sets cached height, which is otherwise got by calling
get_info. Since get_info is called upon needing to display a prompt
after a command has finished, it can be used to determine how much
time a given command took to run if the cache timeout lapses while
the command runs. Refreshing caches the height as a side effect, so
get_info will never be called as a result of displaying a prompt
after refreshing (and potentially leaking how much time it took to
process a set of transactions, therefore leaking whether we got
some monero in them).
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