/**
 * The base branch a checkout is measured against, and how far a revision
 * trails it (T14007).
 *
 * One home for "origin's default branch": change-set, affected-packages and
 * gate-runner each carried their own copy, and NEXUS freshness needs the same
 * answer to say how many commits an index is behind.
 *
 * Code placed in `packages/core/` per Package-Boundary Check — verified against AGENTS.md.
 *
 * @module git/base-ref
 * @task T14007
 */
/**
 * `origin/<default>` from `refs/remotes/origin/HEAD`, else `origin/main` or
 * `origin/master` when that remote branch exists.
 *
 * @param root - Repository to ask.
 * @returns The remote-tracking ref, or `null` when origin has no default branch here.
 * @example
 * ```ts
 * resolveOriginDefault('/repo'); // 'origin/main'
 * ```
 */
export declare function resolveOriginDefault(root: string): string | null;
/**
 * The ref a checkout's freshness is measured against: origin's default branch,
 * else a local `main` or `master`, else `HEAD` (a remote-less repository).
 *
 * @param root - Repository to ask.
 * @returns The ref, or `null` when `root` is not a git repository with a commit.
 * @example
 * ```ts
 * resolveBaseRef('/repo'); // 'origin/main'
 * ```
 */
export declare function resolveBaseRef(root: string): string | null;
/**
 * The commit a ref names.
 *
 * @param root - Repository to ask.
 * @param ref - Ref or revision.
 * @returns The full sha, or `null` when it does not resolve.
 */
export declare function revParse(root: string, ref: string): string | null;
/**
 * Commits reachable from `to` but not from `from` (`git rev-list --count from..to`).
 *
 * @param root - Repository to ask.
 * @param from - The older revision (e.g. an index's revision).
 * @param to - The newer revision (e.g. the base branch).
 * @returns The count, or `null` when either revision is unknown here.
 * @example
 * ```ts
 * commitsBetween('/repo', indexedSha, 'origin/main'); // 3239
 * ```
 */
export declare function commitsBetween(root: string, from: string, to: string): number | null;
/**
 * Tracked files that differ between `rev` and the working tree (`git diff
 * --name-only rev`), counted without walking the tree (T14014).
 *
 * @param root - Repository to ask.
 * @param rev - The revision to compare against (e.g. an index's revision).
 * @returns The count, or `null` when `rev` is unknown here.
 * @example
 * ```ts
 * changedFilesSince('/repo', indexedSha); // 2656
 * ```
 */
export declare function changedFilesSince(root: string, rev: string): number | null;
/**
 * The merge-base of HEAD and origin's default branch: where the branch's own
 * commits begin.
 *
 * @param root - Repository to ask.
 * @returns The merge-base commit, or `null` when there is no origin default
 *   branch or git fails.
 */
export declare function originDefaultMergeBase(root: string): string | null;
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