code: def add_parser(subparsers, parent_parser):
      DIFF_DESCRIPTION = (
          "Show added, modified, or deleted data between commits in the DVC"
          " repository, or between a commit and the workspace."
      )
      diff_parser = subparsers.add_parser(
          "diff",
          parents=[parent_parser],
          description=append_doc_link(DIFF_DESCRIPTION, "diff"),
          help=DIFF_DESCRIPTION,
          formatter_class=formatter.RawDescriptionHelpFormatter,
      )
      diff_parser.add_argument(
          "--targets",
          nargs="*",
          help="Specific DVC-tracked files to compare. Accepts one or more file paths.",
          metavar="<paths>",
      ).complete = completion.FILE
      diff_parser.add_argument(
          "a_rev",
          help="Old Git commit to compare (defaults to HEAD)",
          nargs="?",
          default="HEAD",
      )
      diff_parser.add_argument(
          "b_rev",
          help="New Git commit to compare (defaults to the current workspace)",
          nargs="?",
      )
      diff_parser.add_argument(
          "--json",
          help="Format the output into a JSON",
          action="store_true",
          default=False,
      )
      diff_parser.add_argument(
          "--show-hash",
          help="Display hash value for each entry",
          action="store_true",
          default=False,
      )
      diff_parser.add_argument(
          "--md",
          help="Show tabulated output in the Markdown format (GFM).",
          action="store_true",
          dest="markdown",
          default=False,
      )
      diff_parser.add_argument(
          "--hide-missing",
          help="Hide missing cache file status.",
          action="store_true",
      )
      diff_parser.set_defaults(func=CmdDiff)
  
file_path: dvc/dvc/commands/diff.py
imports: import os
  from dvc.cli import completion, formatter
  from dvc.cli.command import CmdBase
  from dvc.cli.utils import append_doc_link
  from dvc.log import logger
  from dvc.ui import ui
label_desc: Use image node_id 3 for calling a global function with example usage: add_parser(subparsers, parent_parser) without return types