** Do a diff against a single file named in g.argv[2] from version zFrom
** against the same file on disk.
*/
static void diff_one_against_disk(const char *zFrom, const char *zDiffCmd){
  Blob fname;
  Blob content;
  file_tree_name(g.argv[2], &fname, 1);
  historical_version_of_file(zFrom, blob_str(&fname), &content);
  historical_version_of_file(zFrom, blob_str(&fname), &content, 0);
  diff_file(&content, g.argv[2], g.argv[2], zDiffCmd);
  blob_reset(&content);
  blob_reset(&fname);
}

/*
** Run a diff between the version zFrom and files on disk.  zFrom might

  const char *zDiffCmd
){
  char *zName;
  Blob fname;
  Blob v1, v2;
  file_tree_name(g.argv[2], &fname, 1);
  zName = blob_str(&fname);
  historical_version_of_file(zFrom, zName, &v1);
  historical_version_of_file(zTo, zName, &v2);
  historical_version_of_file(zFrom, zName, &v1, 0);
  historical_version_of_file(zTo, zName, &v2, 0);
  diff_file_mem(&v1, &v2, zName, zDiffCmd);
  blob_reset(&v1);
  blob_reset(&v2);
  blob_reset(&fname);
}

/*