phabricator/src/applications/diffusion/query/rawdiff/DiffusionMercurialRawDiffQuery.php

<?php

final class DiffusionMercurialRawDiffQuery extends DiffusionRawDiffQuery {

  protected function newQueryFuture() {
    $drequest = $this->getRequest();
    $repository = $drequest->getRepository();

    $commit = $this->getAnchorCommit();

    // If there's no path, get the entire raw diff.
    $path = nonempty($drequest->getPath(), '.');

    $against = $this->getAgainstCommit();
    if ($against === null) {
      // If `$commit` has no parents (usually because it's the first commit
      // in the repository), we want to diff against `null`. This revset will
      // do that for us automatically.
      $against = hgsprintf('(%s^ or null)', $commit);
    }

    $future = $repository->getLocalCommandFuture(
      'diff -U %d --git --rev %s --rev %s -- %s',
      $this->getLinesOfContext(),
      $against,
      hgsprintf('%s', $commit),
      $path);

    return $future;
  }

}