/**
 * Revalidation cache for the `cleo complete` evidence staleness check
 * (T12102 / gh#1196).
 *
 * `cleo complete` re-validates every hard evidence atom recorded at
 * `cleo verify` time (ADR-051 Decision 8 — `E_EVIDENCE_STALE` catches
 * post-verify tampering). On large repos the per-atom git spawns make a
 * loop of completes slow enough to blow agent tool timeouts.
 *
 * ## What is cached, and why it is safe
 *
 * Only `commit:` atom revalidation is cached, keyed on
 * `(commitSha, headSha)`. Every check {@link validateCommit} performs on
 * the complete-time path (no `taskId`) is an IMMUTABLE fact of the git
 * object DAG once both SHAs are fixed:
 *
 *   - `git cat-file -e <sha>^{commit}` — object existence is immutable
 *     (objects are never removed from a live repo by ordinary work).
 *   - `git merge-base --is-ancestor <sha> <headSha>` — reachability
 *     between two fixed commits can never change.
 *   - `git rev-parse [--short] <sha>` — canonicalisation is immutable.
 *
 * A new commit moves `HEAD`, which changes the key, so post-verify
 * commits always force a fresh validation. Only successful validations
 * are cached: a "commit not found" failure is NOT immutable (a later
 * `git fetch` can make the object appear), so failures always re-run.
 *
 * ## What is deliberately NOT cached
 *
 *   - `files:` / `test-run:` — the staleness guarantee IS the
 *     read-the-file-and-compare-sha256 step. Any cheaper key (mtime +
 *     size) is forgeable and would silently weaken `E_EVIDENCE_STALE`,
 *     which is the entire point of re-validation. These atoms stay
 *     uncached; their cost is one read + one hash per path.
 *   - `tool:` — never re-executed at complete time by design (see
 *     {@link revalidateEvidence}); verify-time results are already
 *     memoised by the ADR-061 cache in tool-cache.ts.
 *
 * Entries live beside the ADR-061 tool cache under
 * `.cleo/cache/evidence/reval-commit-<key>.json` so `clearToolCache`
 * wipes them too — the cache is purely advisory.
 *
 * @task T12102 (gh#1196)
 * @adr ADR-051
 * @adr ADR-061
 */
/**
 * One cached `commit:` atom revalidation. Success-only by design — see
 * the module docstring for the immutability argument.
 *
 * @task T12102
 */
export interface CommitRevalidationEntry {
    /** Schema version for forwards compatibility. */
    schemaVersion: 1;
    /** Discriminator so a foreign JSON blob is never trusted. */
    kind: 'commit-revalidation';
    /** Cache key (also encoded in the filename). */
    key: string;
    /** Canonical full commit SHA that validated successfully. */
    sha: string;
    /** Abbreviated SHA captured at validation time. */
    shortSha: string;
    /** `HEAD` SHA the reachability check ran against. */
    head: string;
    /** ISO 8601 wall-clock timestamp of the validation. */
    capturedAt: string;
}
/**
 * Compute the cache key for a `(commitSha, headSha)` pair.
 *
 * Mirrors the ADR-061 key style: sha256 of the JSON payload, truncated
 * to 32 hex chars — collision-resistant and bounded regardless of input.
 *
 * @task T12102
 */
export declare function computeCommitRevalidationKey(commitSha: string, headSha: string): string;
/**
 * Absolute path for a revalidation cache entry by key.
 *
 * @task T12102
 */
export declare function commitRevalidationPath(projectRoot: string, key: string): string;
/**
 * Read a cached commit-revalidation entry. Returns `null` when the entry
 * is missing, unreadable, schema-incompatible, or keyed differently
 * (defence against a poisoned cache directory).
 *
 * @task T12102
 */
export declare function readCommitRevalidationEntry(projectRoot: string, key: string): CommitRevalidationEntry | null;
/**
 * Atomically write a cache entry: tmp-then-rename so concurrent readers
 * never observe a half-written file (same discipline as tool-cache.ts).
 *
 * @task T12102
 */
export declare function writeCommitRevalidationEntry(projectRoot: string, entry: CommitRevalidationEntry): void;
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