/**
 * Returns a unified diff using the system's git, comparing two paths even if not in a repo.
 * Uses `git diff --no-index` so neither path needs to be tracked by git.
 *
 * Exit codes: 0 (no changes), 1 (changes), >1 (error). We treat 0/1 as success.
 * Throws if git is unavailable or another error occurs.
 */
export declare function getGitUnifiedDiff(oldPath: string, newPath: string): Promise<string>;