Use of rsync inside generated build.sh prevents usage with readthedocs

[ssbarnea]

To build with RTD, we will need to make use of custom build commands, aka build.commands feature, one that is highly promoted by them (aiming to become the default very soon).

Still, this feature comes with one major downside, losing ability to use apt_packages (and sudo is not available either).

All VM images provided by RTD do not have rsync installed and they do not want to install it.

This means that in its current form antsibull-docs cannot be integration with RTD, which is currently the most common system that allows to test pull-requests changes made to documentation.

I do think that we might need to find a way to make rsync optional in build.sh, falling back to a plain old copy instead.

References:

• Installing rsync by default readthedocs/readthedocs.org#11219
• build.commands shall support custom package installation (build.apt_packages) readthedocs/readthedocs.org#9599
• Add docs building and testing ansible/event-driven-ansible#276

[felixfontein]

This again is not a bug, but an enhancement.

[ssbarnea]

@felixfontein We could argue four hours about what makes an issue a feature, bug or fug but that is better over a glass of beer. It becomes funny when a design flaw becomes a feature, just because the original design missed to cover that aspect. 🍻

[felixfontein]

@ssbarnea it's pretty simple. If a feature works as designed, it's not a bug, but a feature / enhancement request. The feature here works as designed. So it's not a bug.