[QGIS-Developer] Backporting and 3.10 -- a reminder

[Nyall Dawson]

Hi list,

Some quick reminders about how the current 3.10 LTR should be handled
during the 3.16 bug fixing round. My apologies in advance about the
tone here, but I feel strong language IS required in order to
reinforce the severity of this message!

1. At this point in time, the 3.10 LTR is mature and we need to take
EXTREME care when backporting fixes to it. Only low risk, high-impact
bug fixes should be backported at this stage. Minor bug fixes or high
risk changes should NOT be backported, and instead should be included
in 3.16 only. !!!!!!!!!!!!!!!!!!!THE RISK OF REPUTATION HARM TO QGIS
CAUSED BY INTRODUCING REGRESSIONS IN 3.10 CANNOT BE
UNDERSTATED!!!!!!!!!!!!!

2. If I wasn't clear enough in (1): DON'T BE SELFISH!. It doesn't
matter how important a minor/high risk bug fix is to YOU/YOUR customer
-- think of all the other millions of users of QGIS who will be
impacted if you introduce a regression!!

3. Matthias Kuhn and I are the acting gatekeepers to the LTR branch.
PSC haven't yet made these roles official, but they DID give us
direction to act in this role for the present. DO NOT MERGE TO LTR
WITHOUT MATTHIAS OR MY APPROVAL. (If you disagree with this, PLEASE
raise objections on the PSC list. But until further direction from PSC
this is the status quo and we'll both be carrying out this role).

4. In order to protect the stability of LTR, Matthias and I introduced
the one-month-delay for backport inclusion policy a few cycles ago.
This has proved very valuable, and has prevented numerous serious
regressions from ever touching the LTR branch. (win!) We'll manage
this process by tagging 3.10 backports with a "NOT FOR MERGE" label,
and then as soon as the backport is approved by someone (which
**doesn't** have to be Matthias or me, it just has to be someone who
isn't the original developer) then the backport will be moved to the
"collected pending backports PR" (eg
https://github.com/qgis/QGIS/pull/38748). We're doing all the hard
work here to keep things easy for you and to keep the PR queue
flowing.

5. The only exceptions to the one-month-delay policy are:
- crash fixes or serious data corruption fixes
- fixes which repair regressions which have been introduced in an LTR
patch release
Backports meeting these criteria can be merged immediately without the
time delay, but again, Matthias and I will manage this.

(and now for the carrot): IMO 3.10 is a great release, and in a very
good state. I'm proud of how mature and stable 3.10 is, and how stable
it is. Let's keep it that way :D

Nyall