How do we maintain the internal documentation links in whatsnew pages ?

[pp-mo]

I didn't even realise this before, but documentation links in old whatsnew comments don't point at "old versions" of those pages, but at the latest version.

Which means if we change the current docs structure so that such a page no longer exists, we get problems, as occurred here : linkcheck output...

/home/runner/work/iris/iris/docs/src/whatsnew/1.7.rst:332: WARNING: unknown document: '/techpapers/index'
/home/runner/work/iris/iris/docs/src/whatsnew/1.7.rst:332: WARNING: unknown document: '/techpapers/um_files_loading'
 . . .

build finished with problems, 2 warnings.
make[1]: *** [Makefile:37: html] Error 1
make[1]: Leaving directory '/home/runner/work/iris/iris/docs/src'
make: *** [Makefile:9: html] Error 2
nox > Command make clean html failed with exit code 2
nox > Session linkcheck failed.
Error: Process completed with exit code 1.

( Aside :

So ... that one was fixed by changing the link to point at the new "further_topics/tech_papers". But if we simply merged the tech-papers into the further-topics list, then that list has no overview page at present, so there would be nothing to point to. )

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The above is really just a demonstration that what an old whatnews link points to won't always remain appropriate (even if it still works).

So for instance, the v1.7 whatsnew page in the v3.7.0 docs build , ( i.e. the link https://scitools-iris.readthedocs.io/en/v3.7.0/whatsnew/1.7.html#documentation ) points to the 'tech papers' section of the v3.7.0 build.

One great solution that seems plausible would be to fix this to point at the "v1.7 tech papers", in the v1.7 build. But unfortunately, we don't have such a build on RTD, since we already determined that the older version docs are now obsolete + it would be far too much work to fix them so they can build with modern Sphinx/RTD. ( in fact, IIRC we removed the old builds, on the old site, to prevent old info coming up in searches )