Function compareStatsAndContent

src/utils/fileHistory.ts:642–674

* Shared stat/content comparison logic for sync and async change checks. * Returns true if the file has changed relative to the backup.

(
  originalStats: Stats | null,
  backupStats: Stats | null,
  compareContent: () => T,
)

 * Returns true if the file has changed relative to the backup.
 */
function compareStatsAndContent<T extends boolean | Promise<boolean>>(
  originalStats: Stats | null,
  backupStats: Stats | null,
  compareContent: () => T,
): T | boolean {
  // One exists, one missing -> changed
  if ((originalStats === null) !== (backupStats === null)) {
    return true
  }
  // Both missing -> no change
  if (originalStats === null || backupStats === null) {
    return false
  }

  // Check file stats like permission and file size
  if (
    originalStats.mode !== backupStats.mode ||
    originalStats.size !== backupStats.size
  ) {
    return true
  }

  // This is an optimization that depends on the correct setting of the modified
  // time. If the original file's modified time was before the backup time, then
  // we can skip the file content comparison.
  if (originalStats.mtimeMs < backupStats.mtimeMs) {
    return false
  }

  // Use the more expensive file content comparison. The callback handles its
  // own read errors — a try/catch here is dead for async callbacks anyway.
  return compareContent()
}

/**
 * Computes the number of lines changed in the diff.