why environ variables like TF_CLI_CONFIG_FILE doesnt work?

I want to run ```terraform init``` with mode offline.because provider download doesnt work.howerer,when i configure terraform.rc ```disable_checkpoint =true```,this variable doesnt work at all

Start by reproducing the reported behavior with `terraform init`, `TF_CLI_CONFIG_FILE`, and `terraform.rc`, focusing on offline provider downloads and `disable_checkpoint`. Trace how terraform-exec invokes the Terraform CLI and verify that the environment variable and configuration are passed through correctly; done means the reported configuration works as expected.

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