stripHash uses a global variable to communicate it's computation
results, but it's not necessary. You can just pipe to stdout in a
subshell. A function mostly behaves like just another command.
baseHash() also introduces a suffix-stripping capability since it's
something the users of the function tend to use.
pin urls to a specific commitish, because in the case the font gets
an update hashes will change on the master and therefore break, as
@zimbatm pointed out in #11574.
