Function getCommitRangeDiff

app/src/lib/git/diff.ts:193–246

(
  repository: Repository,
  file: FileChange,
  commits: ReadonlyArray<string>,
  hideWhitespaceInDiff: boolean = false,
  useNullTreeSHA: boolean = false
)

 *
 */
export async function getCommitRangeDiff(
  repository: Repository,
  file: FileChange,
  commits: ReadonlyArray<string>,
  hideWhitespaceInDiff: boolean = false,
  useNullTreeSHA: boolean = false
): Promise<IDiff> {
  if (commits.length === 0) {
    throw new Error('No commits to diff...')
  }

  const oldestCommit = useNullTreeSHA ? NullTreeSHA : commits[0]
  const oldestCommitRef = useNullTreeSHA ? NullTreeSHA : `${commits[0]}^`
  const latestCommit = commits.at(-1) ?? '' // can't be undefined since commits.length > 0
  const args = [
    'diff',
    oldestCommitRef,
    latestCommit,
    ...(hideWhitespaceInDiff ? ['-w'] : []),
    '--patch-with-raw',
    '--format=',
    '-z',
    '--no-color',
    '--',
    ensureRelativePath(file.path),
  ]

  if (
    file.status.kind === AppFileStatusKind.Renamed ||
    file.status.kind === AppFileStatusKind.Copied
  ) {
    args.push(ensureRelativePath(file.status.oldPath))
  }

  const result = await git(args, repository.path, 'getCommitsDiff', {
    encoding: 'buffer',
    expectedErrors: new Set([GitError.BadRevision]),
  })

  // This should only happen if the oldest commit does not have a parent (ex:
  // initial commit of a branch) and therefore `SHA^` is not a valid reference.
  // In which case, we will retry with the null tree sha.
  if (result.gitError === GitError.BadRevision && useNullTreeSHA === false) {
    return getCommitRangeDiff(
      repository,
      file,
      commits,
      hideWhitespaceInDiff,
      true
    )
  }

  return buildDiff(result.stdout, repository, file, latestCommit, oldestCommit)
}

/**
 * Get the files that were changed for the merge base comparison of two branches.