We don't have docs for how to upgrade Mercurial in CI. A lot of it
is organic institutional knowledge that lives in various people's
heads. That's not good for continuity of business.
This commit starts to establish documentation for how to upgrade
Mercurial in Firefox CI.
The documentation for updating things in-tree is pretty robust
(because I've done it a handful of times and know what is involved).
But the docs for OpenCloudConfig and Puppet could certainly be
improved. I'll poke the respective maintainers of these systems
to help improve these docs as a follow-up.
MozReview-Commit-ID: Aruh3N8Llls
--HG--
extra : rebase_source : 5d82ffd1d2b808082d824274db33586f71899599
Sylvestre Ledru
Gregory Szorc