Add documentation for all possible environment variables

[nbraun-wolf]

Hi,

please document all enviroment variables in https://pip.pypa.io/en/stable/topics/configuration/#environment-variables. Currently there are only 2 listed but I know that there is at least one more PIP_EXTRA_INDEX_URL.

Cheers

[pfmoore]

The docs say "pip’s command line options can be set with environment variables using the format PIP_<UPPER_LONG_NAME>". If you refer to the list of options, this tells you what environment variables are supported.

Adding a list in the environment variables section as well will simply duplicate information that is already available, and will add a maintenance burden keeping the two lists in line.

If however, there is a way that we can clarify the existing text so that it would have been clearer to you that the existence of --extra-index-url meant that the environment variable PIP_EXTRA_INDEX_URL was supported as well, we'd love to hear suggestions for better wording 🙂

[nbraun-wolf]

I guess that's ok but it would be good to add all flags then to that page. If neither one is fully listed, it isn't duplication. If they are on some other page, which I couldn't find so far, then putting them on the same page would help to be more clear. I have also tried with the search function https://pip.pypa.io/en/stable/search/?q=flags&check_keywords=yes&area=default

[uranusjr]

A list of environment variables (and potentially config file sections and keys) would indeed be useful since it is really not easy to discover them unless you internalise all the mapping rules (which I’m pretty sure 99.99% of pip users don’t). The difficulties here is that they are inferred automatically from pip options (which are automatically documented from pip’s source code), so it’d be a giant chore manually keeping the list up-to-date. The solution must be something machine-generated, i.e. a Sphinx plugin.

[pradyunsg]

Closing as a duplicate of #8044