offline install failed due to git ls-remote unable to access github; as well as --prefer-offline config not works in .yarnrc

[LouisSung]

I realize that yarn 2.x has been released, I'll give it a try later

For now, I'm adopting the yarn@1.22.5 to Rocket.Chat in order to gain the offline installation feature
I've set up the cache-folder and yarn-offline-mirror, which can really keep the local files correctly (as shown in screenshot)
However, the yarn still try to invoke the git ls-remote even when running in the offline mode when yarn.lock file exists (without node_modules)

Besides, I tired to adopt --prefer-offline to all of the yarn install and yarn add commands with .yarnrc like mentioned in #6398
However, I've already tried the install.prefer-offline true, install.prefer-offline "", "--install.prefer-offline" true, install.prefer-offline "--dummy", etc. that any combination I could think of, and NON of them work :(
Does this feature still work in yarn@1.22.5 ?

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1. I wonder if there's any mechanism to bypass the git ls-remote or to ignore it (just keep running instead of force stop)
2. How to set up default --prefer-offline with .yarnrc

Thank you very much :)

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Environment:

1. In Docker image (FROM node:12.22.1-buster-slim), simulate offline environment by docker run --network none
   • I could provide the Dockerfile I wrote if anyone need one (not commit and push yet)
2. With/without using root user reach this error
3. With/without keeping the yarn.lock reach this error too