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ci: fix migration-policy false positives from shallow base fetch #9

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Merged
thedancingdeveloper merged 1 commit into from
Aug 24, 2026
Merged

ci: fix migration-policy false positives from shallow base fetch #9

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13 changes: 11 additions & 2 deletions ci/migration-policy.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,17 @@ if [[ -n "$workflow_matches" ]]; then
fail 'workflow selects a hosted or unresolved dynamic runner'
fi
if [[ -n "${GITHUB_BASE_REF:-}" ]]; then
git fetch --no-tags --depth=1 origin "$GITHUB_BASE_REF" >/dev/null 2>&1 || true
commits="$(git rev-list --reverse "origin/$GITHUB_BASE_REF..HEAD" 2>/dev/null || git rev-list --reverse HEAD~1..HEAD 2>/dev/null || git rev-list --reverse HEAD)"
# Fetch the base ref with full history (not --depth=1): a shallow base ref
# grafts away its ancestry, so `origin/BASE..HEAD` can no longer tell that
# the base tip's ancestors are shared with HEAD. On a branch that has merged
# the base in (e.g. after "Update branch"), that made historical base commits
# reappear in the range as false positives.
git fetch --no-tags origin "$GITHUB_BASE_REF" >/dev/null 2>&1 || true
# Scope to commits this PR actually introduces: everything since the branch
# diverged from the base (merge-base), which excludes commits merged in from
# the base itself.
base="$(git merge-base "origin/$GITHUB_BASE_REF" HEAD 2>/dev/null || true)"
commits="$(git rev-list --reverse "${base:+$base..}HEAD" 2>/dev/null || git rev-list --reverse HEAD~1..HEAD 2>/dev/null || git rev-list --reverse HEAD)"
elif [[ "${GITHUB_EVENT_NAME:-}" == push && "${GITHUB_BEFORE:-}" != 0000000000000000000000000000000000000000 ]]; then
commits="$(git rev-list --reverse "${GITHUB_BEFORE:-}..HEAD" 2>/dev/null || git rev-list --reverse HEAD~1..HEAD 2>/dev/null || git rev-list --reverse HEAD)"
else
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