From: Ralph Corderoy <ralph@inputplus.co.uk>
Date: Sun, 16 Oct 2016 14:25:37 +0000 (+0100)
Subject: Don't test -reverse's boolean on every message number.
X-Git-Url: https://diplodocus.org/git/nmh/commitdiff_plain/cfb5a32c4e47d9061ced49e74f34c275bd9e4b54?ds=sidebyside;hp=cfb5a32c4e47d9061ced49e74f34c275bd9e4b54

Don't test -reverse's boolean on every message number.
Test just once before the loop and define start, end, and increment.
Keep going whilst start is not end.  Happy for underflow or overflow in
calculating end because msgnum will make the same transition.  It can't
affect whether the loop runs at all since 0 is not a valid message
number.
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