Function computeDiffStatsForFile

src/utils/fileHistory.ts:677–723

* Computes the number of lines changed in the diff.

(
  originalFile: string,
  backupFileName?: string,
)

 * Computes the number of lines changed in the diff.
 */
async function computeDiffStatsForFile(
  originalFile: string,
  backupFileName?: string,
): Promise<DiffStats> {
  const filesChanged: string[] = []
  let insertions = 0
  let deletions = 0
  try {
    const backupPath = backupFileName
      ? resolveBackupPath(backupFileName)
      : undefined

    const [originalContent, backupContent] = await Promise.all([
      readFileAsyncOrNull(originalFile),
      backupPath ? readFileAsyncOrNull(backupPath) : null,
    ])

    if (originalContent === null && backupContent === null) {
      return {
        filesChanged,
        insertions,
        deletions,
      }
    }

    filesChanged.push(originalFile)

    // Compute the diff
    const changes = diffLines(originalContent ?? '', backupContent ?? '')
    changes.forEach(c => {
      if (c.added) {
        insertions += c.count || 0
      }
      if (c.removed) {
        deletions += c.count || 0
      }
    })
  } catch (error) {
    logError(new Error(`FileHistory: Error generating diffStats: ${error}`))
  }

  return {
    filesChanged,
    insertions,
    deletions,
  }
}

function getBackupFileName(filePath: string, version: number): string {
  const fileNameHash = createHash('sha256')