Summary

Diagnosed and fixed two root causes of a ~50s "Install Test Monitor" delay on iOS/tvOS/watchOS simulators (macOS native was unaffected).

Root cause 1: Environment.init blocking on git fetch (~16s)

DDTestMonitor.env is a lazy static property. Its first access in installTestMonitor() triggered Environment.init(), which synchronously called mergeHeadInfo(). That function runs git fetch --deepen=1 to populate commit author/message metadata. On CI simulators with shallow clones or restricted network access, this fetch times out (~16s).

Fix:

• Removed mergeHeadInfo from Environment.init()
• Added Environment.fetchMergeHeadInfo(log:) instance method
• Added DDTestMonitor.loadGitCommitInfo() which schedules the fetch as the first operation on gitUploadQueue
• The git upload operation gets a dependency on the merge-head operation, ensuring env.git is fully populated before uploading
• updateTracerConfig waits for mergeHeadOperation after the settings response (full queue drain if ITR requires git upload, just the merge-head op otherwise)
• Also moved GitUploader.statusUpToDate (a git status subprocess) into the queue operation so it no longer blocks startup

Root cause 2: GithubCIEnvironmentReader.getJobId scanning huge directory tree (~26s)

GithubCIEnvironmentReader.read() calls getJobId() which expands /**/_diag glob patterns by recursively walking /Users/runner/actions-runner/. On a CI machine this directory tree can be very large, causing FileManager.contentsOfDirectory to iterate thousands of entries.

Fix: Added a maxWildcardDepth=3 cap to expandGlobSegments. The _diag directory is always 1–2 levels deep, so all legitimate paths are still found.

Additional improvements

• Added Log.measure timing around all waitUntilAllOperationsAreFinished() calls (instrumentationWorkQueue drain, gitUploadQueue drain, testOptimizationSetupQueue drain)
• Added granular timing inside Environment.init (env-testBundle, env-parallelizationDisabled, env-deviceInfo, env-ciReaders, env-gitInfoAt, etc.)
• Per-reader timing in the CI reader loop
• mergeHeadInfo wrapped in Log.measure
• gitStatusUpToDate wrapped in Log.measure

Test plan

• Run iOS Simulator tests and verify "Install Test Monitor" drops from ~50s to ~2s
• Verify commit author/message metadata still appears in test spans (mergeHeadInfo completes before session start via queue drain in setupCrashHandler)
• Verify ITR git upload still works (upload depends on mergeHead, settings waits for full queue when requireGit)
• Verify GitHub Actions job ID is still reported correctly (glob depth=3 covers all real runner layouts)
• Build passes on iOS Simulator, watchOS, macOS

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