[SDK Validation] replace spawnSync pwsh with simple-git in getChangedFiles to fix ENOBUFS on large PRs

[raych1]

Problem

The spec-gen-sdk-runner's getChangedFiles function uses spawnSync to invoke PowerShell (pwsh) for git diff, which has a default maxBuffer of 1MB. For PRs with thousands of changed files, the output exceeds this buffer limit, causing an ENOBUFS error.

When this happens, runPowerShellScript returns undefined, which gets coalesced to an empty array (?? []). The pipeline then sees 0 changed files and skips SDK validation entirely — reporting a false-positive success.

Pipeline log

Error executing PowerShell script: Error: spawnSync pwsh ENOBUFS
No files changed in the PR
Changed files in the PR: 0
No relevant files changed under 'specification' folder in the PR

Fix

Replace the PowerShell-based getChangedFiles in eng/tools/spec-gen-sdk-runner/src/utils.ts with the existing getChangedFiles from @azure-tools/specs-shared/changed-files, which:

• Uses simple-git (streaming spawn) instead of spawnSync — no buffer size limitation

[github-actions]

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[Copilot]

Pull request overview

This PR fixes a false-positive success scenario in spec-gen-sdk-runner where large PRs with thousands of changed files could trigger an ENOBUFS error from PowerShell's spawnSync-based getChangedFiles. The undefined return from the failed script was silently coalesced to an empty array, causing the SDK validation step to be skipped while reporting success. The fix replaces the PowerShell approach with the existing simple-git-based implementation from @azure-tools/specs-shared/changed-files, which uses streaming and has no buffer size limit.

Changes:

• Replaced the PowerShell-based getChangedFiles in utils.ts with an async wrapper around the shared getChangedFilesShared from @azure-tools/specs-shared/changed-files
• Propagated the async change through detectChangedSpecConfigFiles in spec-helpers.ts and its call site in commands.ts
• Updated all tests to use mockResolvedValue and async/await to match the new async API

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
eng/tools/spec-gen-sdk-runner/src/utils.ts	Replaces PowerShell spawnSync-based getChangedFiles with an async wrapper over the shared simple-git implementation
eng/tools/spec-gen-sdk-runner/src/spec-helpers.ts	Adds async/await to detectChangedSpecConfigFiles to handle the now-async getChangedFiles
eng/tools/spec-gen-sdk-runner/src/commands.ts	Adds await to the detectChangedSpecConfigFiles call
eng/tools/spec-gen-sdk-runner/test/spec-helpers.test.ts	Updates all test cases to use mockResolvedValue and await for the async detectChangedSpecConfigFiles
eng/tools/spec-gen-sdk-runner/test/commands.test.ts	Updates detectChangedSpecConfigFiles spy mocks from mockReturnValue to mockResolvedValue