[automated] Investigate renamed-file handling in selective PR CI

[automated] PR #19486 showed that a same-commit rename can expose the old path as an unmatched deletion and safely fall back to ALL.

The investigation found that exempting unmatched old paths is unsafe: a directory rule can have consumers beyond the moved file, and the destination can be ignored or removed by prefiltering. Either case could silently under-select tests. The selector should therefore retain the run-all fallback.

PR #19790 contains adjacent safety fixes found during the investigation. Both selector layers now share NUL-delimited diff parsing, literal backslashes are preserved, raw paths are escaped for Markdown, and truncated diff streams fail loudly. It deliberately does not suppress the safe ALL result for PR #19486.

Reproduce the renamed-file fallback.
Evaluate whether old rename paths can be safely exempted.
Retain and document the safe run-all behavior.
Land fix(ci): PR test selector could silently mis-attribute changed paths containing tabs or newlines #19790.

David Pine (@IEvangelist)

🤖 Aspire triage pass — 2026-08-28 22:33 UTC

Area: area-engineering-systems
Kind: bug
Repro: yes-large — repeatable example referenced in PR #19486
Affected version(s): N/A — internal selective-test CI selector (not a shipped product surface)
Severity: S4 — selector falls back to running ALL tests, i.e. fails safe (no missed coverage); efficiency-only, fix already in flight (#19790)

Urgency: ⚪ backlog — no milestone
Reason: internal CI selector bug with a safe fallback; not a customer-facing regression, and the fix is already open in #19790

Suggested owner(s): David Pine (@IEvangelist) (score 24), backup Adam Ratzman (@adamint) (score 12)
Evidence:

IEvangelist merged Fix docs safe-output base resolution #19446, Fix gh-aw v0.86.2 safe-output base parsing #19445, Upgrade gh-aw compiler to v0.86.2 #19438, Fix PR docs recovery base handling #19236 in area-engineering-systems (last 90d, 8 PRs)
adamint merged Remove pipeline-scoped Publish-Build-Assets group #19518, Avoid MongoDB credential false positive #19305, Re-enable VS Code extension E2E tests in CI #19142 in area-engineering-systems (last 90d, 4 PRs)
(issue author excluded from owner scoring; no source file paths cited so CODEOWNERS not scored)

Confidence: medium
Needs human?: no

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[automated] Investigate renamed-file handling in selective PR CI #19786

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[automated] Investigate renamed-file handling in selective PR CI #19786

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joperezr commented on Aug 28, 2026

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