Add "no progress" and "no ANSI" environment variables

[aelij]

Summary

Allow disabling progress and ANSI using environment variables.

Background and Motivation

When Copilot runs tests, displaying progress and ANSI are just a waste of tokens. It's possible to configure Copilot's terminal using chat.tools.terminal.terminalProfile.<os> and define environment variables. For example:

{
  "chat.tools.terminal.terminalProfile.windows": {
    "icon": "copilot",
    "path": "pwsh",
    "env": {
      "MSBUILDTERMINALLOGGER": "off"
    }
  }
}

Proposed Feature

Add TESTINGPLATFORM_NOPROGRESS and TESTINGPLATFORM_NOANSI as defaults (overridable by CLI args).

[Youssef1313]

Should we instead detect LLM environments similar to https://github.com/dotnet/sdk/blob/1e5d8e39d3026edb222cdf4f8d8240f1eb99f24b/src/Cli/dotnet/Telemetry/LLMEnvironmentDetectorForTelemetry.cs ?

[aelij]

@Youssef1313 Thanks for a quick solution, however this doesn't work inside VS Code. I tried running the code from the PR inside a shell created by Copilot and it retuned false. VS Code doesn't seem to inject env vars indicating it's a copilot session. Of course I could inject one of those env vars using chat.tools.terminal.terminalProfile, but the detector won't work OOB.

[Youssef1313]

Indeed. Looks like VSCode Copilot doesn't set any of these env vars.

[aelij]

Maybe we should ask VS Code to add an env var

[Youssef1313]

microsoft/vscode#307136