Docs are always completely rebuild

[maxnoe]

Gammapy version

Current main branch.

Bug description

Building the docs is currently an extremely slow process, since even if only small things in the source file are changed, the full documentation is rebuild due to sphinx detecting a change in the extensions, which I don't understand:

updating environment: [extensions changed ('0')] 554 added, 0 changed, 0 removed

Expected behavior
Sphinx only needs to rebuild files which have actually changed.

To Reproduce

Type make -C docs html, wait an eternity, type make -C docs html again: the full documentation is rebuild instead of saying:
"nothing to do".

Other information

I think this might related to the sphinx-astropy? Not sure though.

[Astro-Kirsty]

@stahanna is this something you could look into for us?

I tried to search but the builds build has the flag '-b' which should not be building completely new each time

[stahanna]

@stahanna is this something you could look into for us?

I tried to search but the builds build has the flag '-b' which should not be building completely new each time

ok, I will have a look