/**
 * Where the file tools put the pre-write copy of a file.
 *
 * Lives in utils because smart_edit and smart_write both make backups, and the
 * fix below was applied to smart_edit only -- so smart_write went on writing
 * `<file>.bak` into the user's repository long after the defect was understood.
 * Measured on this checkout: three stray .bak files, including one beside a
 * test fixture and one beside a hook that is regenerated by a sync script.
 *
 * The backup used to be written NEXT TO THE ORIGINAL. That leaves an untracked
 * `README.md.bak` in `git status`, one `git add -A` from being committed, and
 * nothing ever deletes it. A safety net that dirties the tree it is protecting
 * is a poor trade.
 *
 * Backups now live under the user's home directory, keyed by a hash of the
 * absolute path so two files sharing a basename cannot collide, and capped so
 * they cannot grow without bound.
 */
/** Default root: outside every working tree, so a backup can never be committed. */
export declare const BACKUP_ROOT: string;
/**
 * The root to write to right now.
 *
 * Read per call rather than captured at import, so a test can redirect it after
 * this module has already been loaded.
 */
export declare function backupRoot(): string;
/** The directory holding one file's backups. Exported so tests can assert on it. */
export declare function backupDirFor(filePath: string): string;
/**
 * Saves content somewhere it cannot do harm.
 *
 * Failure is never allowed to fail the operation -- the backup is a
 * convenience, the write is the job. But the RETURN VALUE is the outcome, not
 * the request: callers used to report `wasBackedUp` from the caller's own
 * option, so a full disk or a read-only home directory produced a result
 * claiming a backup that was never written. That is precisely the moment
 * somebody relies on it.
 *
 * @returns true only if a backup file is actually on disk.
 */
export declare function writeBackup(filePath: string, content: string, encoding?: BufferEncoding): boolean;
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