"cmake -E copy" if you really need a copy instead of adding it to svn twice and risk it getting out of sync.

Why not use debian rust package? (reproducibility)

You removed the config file.

Pretty harsh, think you don't need such a recent version, maybe 3.15 or so. Using 3.25 Debain bookworm users could build it locally at least. Though using 3.27 for using the existing doxygen config file would be an option, then users could still build the docs as they currently do.

This are only docs, think the name should reflect this.

Is this logo not in svn yet?

IIRC that's a copy paste of the other docker where we had an issue with too old rust for Spidermonkey. Agree at least specifying a version would be better.

Is that needed? Can it output in the HTML folder?

Given the space on the machine, I hope we don't need to pull another image :/

Needed is maybe a to strong a word, but out of tree build is certainly recommended for when using a build system.

I suppose this one would replace the gcc7-docs one, just that the version of this file on the CI is not the one this diff is made against. But you are correct in that it might mean some increase in size all the same.

Maybe you can commit the latest one, so this patch can be rebased?

That's still in the tree just one level down.

In this case this means more images on the disk (debian + build base with new debian + gcc build based on that and docs based on gcc build)

Well, source and build dir are different and build dir isn't an existing dir either. So yes not literally out of tree but to my understanding it's also used like this. Then you have in tree and vpath builds to complement the set, right?

So you prefer a docs image based on build-base with a recent cmake built from source or maybe a prebuilt one from cmake.org to save on disk space?

To be fair I don't mind much since it's gonna get purged by zfs anyway. Mostly keeping the keep the patch as simple as possible unless you really need to ^°

Ideally yes. The smaller the incremental images the better.