RFR: Make trees work with hg 4.6

[Martin Buchholz]

On Thu, Jun 7, 2018 at 11:46 AM, Erik Joelsson <erik.joelsson at oracle.com>
wrote:

> This is because the last two release candidate tags in the official hg
> repo are "4.6rc1" and "4.6rc2". They changed the pattern. I don't see "rc"
> anywhere else in tags that shouldn't be matched. This plugin is only used
> internally in trees testing.
>
> -    tags = filter(lambda t: not t.endswith('-rc') and t != "tip", tags)
> +    tags = filter(lambda t: 'rc' not in t and t != "tip", tags)
>
> The other changes look good to me but I'm not a python or trees developer.
>
>
Ohh.... verlist is being used to get tags for the upstream mercurial repo
for mercurial itself?  If so, maybe document that?

Looking for the substring "rc" seems particularly brittle because it
happens to match "mercurial".