Remove drupal/legacy-project as a starting point for Drupal 10

Moved to MR

I applied patch 14 and corrected wrapping and a duplicate letter. Attached is a diff.

Looks ready

Are we going to do this in the D10 cycle or should we wait until 11.x is open for development and remove it only in 11.x releases?

If #10 is correct we need to actually stop trying to create tarball releases of core via the packaging script altogether, before we break them.

I believe tarball packaging depends on this https://git.drupalcode.org/project/drupalorg/-/blob/2647a1a82a012af30376...

And we’d have to check if this is hard-coded anywhere in subtree splitting, https://bitbucket.org/drupalorg-infrastructure/subtree-splitter/src/master/

@drumm from the DA end what do you think about removing core tarball packaging from 11.x onwards? We'd need to keep the 10.x tarballs probably, unless we do it purely by a date cut-off.

Sure, either policy works. We can get the packaging pipeline, including subtree splits, running on staging and try out this change, so we have less of a chance of debugging in production.

I posted to #3285191-18: [meta] Deprecate tarballs, because they are incompatible with Composer-managed dependencies, Automatic Updates, Project Browser, and release managers' health → a prominent place we’ll need to update, https://www.drupal.org/download →

I tried out the subtree splitter a bit on staging with the diff from the MR. As far as I can tell, it works okay.

The subtree splitter is not a blocker.

I expect more of the parent plan needs to be done before proceeding, this seems like one of the final steps, so leaving this postponed.