Add a conda-forge mirrored_channel

[IsabelParedes]

This PR adds https://prefix.dev/conda-forge as a backup to the default conda-forge channel for a more robust installation.

[hmaarrfk]

I would like @wolfv 's thumbs up on this before I start to consider.

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Here is the question I have:

Q: Does this change mean that I would be downloading TWO repo datas?

Backstory:

• My general "annoyance" with conda/mamba is that they keep downloading 40MB of "repodata".
• When I am in the office, that takes like 10 seconds.
• When I am on a hotspot it is painfully slow to do this when my package is "already in my cache" or "less than 1MB in size".

[SylvainCorlay]

Q: Does this change mean that I would be downloading TWO repo datas?

It only downloads one repodata. It fall backs to prefix.dev on a per-file basis.

[millsks]

Will this affect users that are on a corporate network that get blocked from public channels? Should they remove the mirrored_channels if they are replacing conda-forge under channels with their internal/private proxy remote? Or should they leave conda-forge as the primary and replace the anaconda and prefix mirrors with their internal/private proxy remotes?

[SylvainCorlay]

Will this affect users that are on a corporate network that get blocked from public channels? Should they remove the mirrored_channels if they are replacing conda-forge under channels with their internal/private proxy remote? Or should they leave conda-forge as the primary and replace the anaconda and prefix mirrors with their internal/private proxy remotes?

This only impacts what it means to get things from "conda-forge".

[millsks]

Thanks @SylvainCorlay. We rebuild the installer with internal settings already in place so the end users don't have to update their condarc locally or on our build pipeline. Thank you for clearing that up!

[hmaarrfk]

Thx for answering my questions.

I would like to leave this open for like 2 weeks to ensure that others stakeholders have time to see it.

[xhochy]

Seems like a reasonable change

[wolfv]

From prefix side, this is totally fine :)

[hmaarrfk]

@isuruf @scopatz any thoughts?
https://github.com/orgs/conda-forge/teams/miniforge

(I'll probably wait an other 2 weeks)

[h-vetinari]

LGTM