/**
 * Thrown when `discoverChangedPhases` cannot compute a git diff against the
 * requested base ref (unresolvable ref, not a git repo, git binary missing,
 * etc). Unlike the best-effort `collectGitDiff` in `./diff.ts` — which
 * degrades to an empty string on any failure because it feeds a "nice to
 * have" context blob — a phase-verification gate that discovers *which*
 * phases changed must never silently reinterpret a real git failure as "no
 * phases changed". Callers are expected to let this propagate and fail the
 * gate loudly rather than catch-and-ignore it.
 */
export declare class GitDiffError extends Error {
}
export interface ChangedPhase {
    phase: string;
    id: string;
    path: string;
}
/**
 * Discover which phase SUMMARY.json files changed (added, copied, modified,
 * or renamed) between `baseRef` and `HEAD`. Throws `GitDiffError` on any git
 * failure instead of degrading to an empty result — see `GitDiffError`.
 */
export declare function discoverChangedPhases(repoRoot: string, baseRef: string): ChangedPhase[];
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