shortest: never emit 0-length prefix even if unique...
shortest: never emit 0-length prefix even if unique
It turned out that the pure version of our code for finding the
shortest unique nodeid prefix would return a 0-length string if that
was unique (because there was at most one revision in the
disambiguation set). That's kind of correct, but it can't be used as
input, so we shouldn't return it. Let's just adjust the given
minlength up to at least 1. This fixes test-template-functions.t,
which was failing in pure mode.
Differential Revision:
https://phab.mercurial-scm.org/D5181
