install the project on RTD

[keewis]

The versions were broken because instead of installing we simply extended sys.path. That way, sphinx is able to find the correct version, but setuptools_scm can't put the version in the METADATA file in the installed egg. Instead, pkg_resources.get_distribution("xarray").version gets its version from a released version of xarray that was pulled in by a dependency (hence the old version in the title bar). To fix that, we need to install before building the documentation.

However, since RTD installs with --upgrade --upgrade-strategy=eager (which upgrades all packages to the most recent version), we can't install using their pip method. The setuptools method doesn't work either because cfgrib pulls in the most recent released version of xarray, and setuptools can't seem to overwrite / uninstall previously installed versions. To work around that, this installs using the pip section in the environment file.

• Closes title bar of docs displays incorrect version #4289

[keewis]

that seems to have fixed the version in the title bar, so this should be ready for review and merge

[max-sixty]

Awesome, thanks @keewis , I know the digging was a lot of work. Great to have this fixed.

[keewis]

thanks for the reviews, @max-sixty and @dcherian