Optimize Azure Pipelines with dynamic detection of DSC resource dependencies (#2135)

Author: Copilot

.build/README.md

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+# DSC Resource Integration Test Optimization
+
+This document describes the script used to dynamically determine whether DSC
+resource integration tests should run in Azure Pipelines.
+
+## What the Script Does
+
+The `Test-ShouldRunDscResourceIntegrationTests.ps1` script analyzes git
+changes between two references and determines if DSC resource integration tests
+need to run. It automatically discovers which public commands are used by DSC
+resources and classes, then checks if any relevant files have been modified.
+
+## How It Works
+
+The script checks for changes to:
+
+1. **DSC Resources**: Files under `source/DSCResources/`
+1. **Classes**: Files under `source/Classes/`
+1. **Public Commands**: Commands that are actually used by DSC resources or
+   classes (dynamically discovered)
+1. **Private Functions**: Functions used by the monitored public commands or
+   class-based DSC resources
+1. **Integration Tests**: DSC resource integration test files under
+   `tests/Integration/Resources/`
+
+## Usage
+
+### Azure Pipelines
+
+The Azure Pipelines task sets an output variable that downstream stages can
+use to conditionally run DSC resource integration tests. The script returns
+a boolean value that the pipeline captures, e.g.:
+
+```yaml
+- powershell: |
+    $shouldRun = ./.build/Test-ShouldRunDscResourceIntegrationTests.ps1 -BaseBranch $targetBranch -CurrentBranch HEAD
+    Write-Host "##vso[task.setvariable variable=ShouldRunDscResourceIntegrationTests;isOutput=true]$shouldRun"
+  displayName: 'Determine if DSC resource tests should run'
+```
+
+Downstream stages reference this output variable using the pattern:
+`dependencies.JobName.outputs['StepName.VariableName']` to gate their
+execution based on whether DSC resource tests should run.
+
+### Command Line
+
+```powershell
+# Basic usage (compares current HEAD with origin/main)
+.build/Test-ShouldRunDscResourceIntegrationTests.ps1
+
+# Custom branches
+.build/Test-ShouldRunDscResourceIntegrationTests.ps1 -BaseBranch 'origin/dev' \
+    -CurrentBranch 'feature-branch'
+```
+
+## Dynamic Discovery
+
+The script automatically discovers public commands used by DSC resources by
+scanning source files, eliminating the need to maintain hardcoded lists.
+This ensures accuracy and reduces maintenance overhead.