[WIP] Add path exclusion for .config directory to CI

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Follow-up to #13214, which added path exclusions for documentation/ and .github/ so that CI doesn't run a full test pass when only non-build files change.

The .config/ directory at the root of the repo (https://github.com/dotnet/msbuild/tree/main/.config) contains tooling configuration (e.g. dotnet-tools.json) that does not affect build output or test results in a meaningful way for these pipelines. Changes to it should be treated the same way as documentation/ and .github/ — they should not trigger full CI runs, and when mixed with other non-build changes, the documentation-only-change check should still consider the change "non-build".

Changes required

1. .vsts-dotnet-ci.yml

Add .config/* to the existing paths.exclude list under trigger. After the change the trigger block should look like:

trigger:
  branches:
    include:
    - main
    - exp/*
    - vs*
  paths:
    exclude:
    - documentation/*
    - .github/*
    - .config/*

Do not add path exclusions for PR builds — same rationale as #13214 (required checks must always run so PRs can go green).

2. azure-pipelines/check-documentation-only-change.yml

Expand the PowerShell pattern that detects non-build files to also recognize files under .config/. The current logic (added in #13214) is:

$isNonBuildFile = ($file -match "^documentation/") -or ($file -match "^\.github/")

Update it to also match .config/:

$isNonBuildFile = ($file -match "^documentation/") -or ($file -match "^\.github/") -or ($file -match "^\.config/")

Update any nearby comments / display name text that enumerates the excluded directories so they mention .config as well. Keep the onlyDocChanged output variable name unchanged — many downstream jobs reference it.

Notes

• Mirror the style and structure of the changes made in Exclude documentation and .github from CI triggers #13214 exactly.
• No other files should need changes.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Add the .config directory to the exclusions added in #13214

Assistant: I'm waiting for your response to the confirmation dialog before I can dispatch the coding agent to open the follow-up PR.

This pull request was created from Copilot chat.

[dotnet-policy-service]

Hello @copilot, I noticed that you’re changing an .swr file or any file under src/Package/MSBuild.VSSetup.. Please make sure to validate this change by an experimental VS insertion. This is accomplished by pushing to an exp/* branch, which requires write permissions to this repo.