On Wed, 2021-07-28 at 16:43 +0100, Richard Purdie via lists.openembedded.org wrote:

I think the challenge is going to be the flag day issue for master branches.
For example, there is code in devtool and other places which knows about the
override character. If we allow mixing the different syntax for master then
those tools need to complicate things by referencing both characters. To try
and preserve what is left of my sanity, I'm starting to think we just require
layers to migrate to the new syntax to continue to work with master. The good
news is that those converted layers should work with dunfell and older releases
where the layer already does that with the backported bitbake syntax update.

If we accept that we need to have a flag day for master use, the question is 
when. We could pick some data well in the future or even post 3.4 however I'm
not sure this buys much and we probably may as well get on and do it.

Given these things, I therefore propose that we should start these changes 
and require it for master, probably relatively quickly within a couple of 
weeks?

I have continued to work on this and I now think we're as ready as we'll ever
be with the core. I have:

* submitted a section for the migration guide documenting the conversion process
* increased the minimum bitbake version for OE-Core
* bumped the local.conf version to require new versions of the config file
* added an error to bitbake if it sees "_append"|"_prepend"|"_remove" in 
variable names which would suggest an unconverted layer. If you use those 
in function names in the datastore that was never a good idea and is no 
longer supported.
* merged compatibility changes back to bitbake 1.50, 1.48 and 1.46
* merged the conversion script to OE-Core
* merged submitted tweaks to the conversion script (thanks Martin!)
* made OE-Core honister only, no longer supporting hardknott
* updated converted layers to be honister compatible
* converted autobuilder-helper to use the new syntax
* ensured all of a-quick builds on the autobuilder
* submitted patches for meta-yocto, meta-gplv2, meta-mingw and bitbake

I plan to merge these various things on Monday (2nd August). After that time,
unconverted layers will no longer work with master.

Cheers,

Richard