Function getWorkingDirectoryDiff

app/src/lib/git/diff.ts:342–401

(
  repository: Repository,
  file: WorkingDirectoryFileChange,
  hideWhitespaceInDiff: boolean = false
)

 * that all content in the file will be treated as additions.
 */
export async function getWorkingDirectoryDiff(
  repository: Repository,
  file: WorkingDirectoryFileChange,
  hideWhitespaceInDiff: boolean = false
): Promise<IDiff> {
  // `--no-ext-diff` should be provided wherever we invoke `git diff` so that any
  // diff.external program configured by the user is ignored
  const args = [
    'diff',
    ...(hideWhitespaceInDiff ? ['-w'] : []),
    '--no-ext-diff',
    '--patch-with-raw',
    '-z',
    '--no-color',
  ]
  const successExitCodes = new Set([0])
  const isSubmodule = file.status.submoduleStatus !== undefined

  // For added submodules, we'll use the "default" parameters, which are able
  // to output the submodule commit.
  if (
    !isSubmodule &&
    (file.status.kind === AppFileStatusKind.New ||
      file.status.kind === AppFileStatusKind.Untracked)
  ) {
    // `git diff --no-index` seems to emulate the exit codes from `diff` irrespective of
    // whether you set --exit-code
    //
    // this is the behavior:
    // - 0 if no changes found
    // - 1 if changes found
    // -   and error otherwise
    //
    // citation in source:
    // https://github.com/git/git/blob/1f66975deb8402131fbf7c14330d0c7cdebaeaa2/diff-no-index.c#L300
    successExitCodes.add(1)
    args.push('--no-index', '--', '/dev/null', file.path)
  } else if (file.status.kind === AppFileStatusKind.Renamed) {
    // NB: Technically this is incorrect, the best kind of incorrect.
    // In order to show exactly what will end up in the commit we should
    // perform a diff between the new file and the old file as it appears
    // in HEAD. By diffing against the index we won't show any changes
    // already staged to the renamed file which differs from our other diffs.
    // The closest I got to that was running hash-object and then using
    // git diff <blob> <blob> but that seems a bit excessive.
    args.push('--', ensureRelativePath(file.path))
  } else {
    args.push('HEAD', '--', ensureRelativePath(file.path))
  }

  const { stdout, stderr } = await git(
    args,
    repository.path,
    'getWorkingDirectoryDiff',
    { successExitCodes, encoding: 'buffer' }
  )
  const lineEndingsChange = parseLineEndingsWarning(stderr)