[BuildStream] Plug-In Strategy: Summary Mail

[Laurence Urhegyi <laurence urhegyi codethink co uk>]

Hello all,

We have discussed the plug-in strategy for BuildStream a lot, (see links 
0 to 3 below) and I think there's a general consensus. I'm not sure that 
we ever actually summarised and agreed though, and I'd like to get the 
public status of this discussion to be 'confirmed, agreed, documented, 
let's action it'. Then we can get on with our plans to make changes, 
which we desperately need because the current situation is not great for 
users. This email is therefore an attempt at a summary that we can agree 
on, and from there make a clear path forward that will please users.

I think we can summarise the discussions as:

* Many plug-ins should be moved into their own domain and their own repo
* We'll start with the bare minimum to be moved out: we've spoken of git 
and python plug-ins coming out of core and of Container plug-ins out of 
bst-external
* We'll therefore need to provide warnings to users that these will be 
deprecated, and we need to land these warnings before 1.4
* We should do the movement and create associated test suites before 1.6 
(the CI here is a challenge but not impossible)
* We'll need a clear policy as part of all this
* For this policy, we basically agreed:
     * Each plug-in needs a dedicated maintainer or maintainers
     * They should decide and declare when it’s stable and the user 
should trust the maintainer of the plug-in
     * We should have a central list of plug-ins which BuildStream can 
recommend (this one is maybe contentious, but not a blocker for any of 
the above)

Does this match other people's understanding of the path forward? I know 
many people are not around at the moment but if there's no objections by 
mid-January then I think we should take this as confirmed.

Thanks,
Laurence

[0] 
https://gitlab.com/BuildStream/nosoftware/communication/blob/master/gatherings/BuildStream_Gathering_2018_minutes.pdf
[1] 
https://mail.gnome.org/archives/buildstream-list/2018-October/msg00057.html
[2] 
https://mail.gnome.org/archives/buildstream-list/2018-November/msg00016.html
[3] 
https://mail.gnome.org/archives/buildstream-list/2018-November/msg00061.html