[QGIS-Developer] Gentle request: please be careful with 2.18 backports

[Nyall Dawson]

Hi all,

This is a gentle request to please please pay very special attention
when backporting fixes to 2.18, and assess carefully whether those
fixes are REALLY necessary in the stable LTR branch. Unfortunately the
last couple of 2.18 patch releases have seen some serious regressions
introduced as a result of backported fixes, which really harms the
reputation of QGIS' stability.

It's no-ones fault, because we ALL make mistakes and create
regressions... but I think at this stage we should tighten up 2.18 now
to only mission critical, very clearly safe bug fixes, and leave all
"minor" fixes for 3.x only.

(Possibly we should consider switching on github branch protection
here, blocking direct commits and requiring a minimum of 2 or 3
'acceptable' reviews from core devs on PRs?)

Nyall