Thanks Ralf.

I think this lost the ones that were inlcuded by the previous generation in #24510? There some smaller fixups on that, but not sure they are relevant, maybe it is easier to just pull in all those fragments again.

Oh great, a tool that silently deletes content. And doesn't even have an option for merging as far as I can tell from https://towncrier.readthedocs.io/en/stable/cli.html#towncrier-build. I only checked one of the first deleted lines in the diff and saw it was moved, so I thought it was a diff display thing and didn't check the whole thing.

I'll fix this up manually, but it looks to me like it makes the tool pretty much useless then.

I think you can get a bit of a work-around by adding a line to the generated file to tell towncrier not to remove the current content. There will still be two heading lines, but they can be deleted in the inevitable cleanup.

Just doing a merge or copying things manually is probably just as well. The point is, towncrier is meant to be run exactly once.
It is running in our devdocs build so we always have a nice rendered version online. The only small wrinkle is that the local docs build shouldn't mutate the repo, so it doesn't run towncrier: Could be done I am sure. Nobody ever asked for it.

gh-25832 should restore the missing content.

I think you can get a bit of a work-around by adding a line to the generated file

Ah good find, that seems needed. I'll see about adding that in the next PR.

The point is, towncrier is meant to be run exactly once. [...] The only small wrinkle is that the local docs build shouldn't mutate the repo, so it doesn't run towncrier

Let's fix that; this isn't a reasonable restriction and not having a local build seems bad (we'd never accept that for code, so I don't think we should for docs either). I'll see if it's easy to do.