code: def test_diff(path=None, norepo=None):
      with chpwd(norepo):
          assert_raises(NoDatasetFound, diff)
      ds = Dataset(path).create()
      assert_repo_status(ds.path)
      # reports stupid revision input
      assert_result_count(
          ds.diff(
              fr="WTF", on_failure="ignore", result_renderer="disabled"
          ),
          1,
          status="impossible",
          message="Git reference 'WTF' invalid",
      )
      # no diff
      assert_result_count(
          _dirty_results(ds.diff(result_renderer="disabled")), 0
      )
      assert_result_count(
          _dirty_results(
              ds.diff(fr="HEAD", result_renderer="disabled")
          ),
          0,
      )
      # bogus path makes no difference
      assert_result_count(
          _dirty_results(
              ds.diff(
                  path="THIS", fr="HEAD", result_renderer="disabled"
              )
          ),
          0,
      )
      # let's introduce a known change
      create_tree(ds.path, {"new": "empty"})
      ds.save(to_git=True)
      assert_repo_status(ds.path)
  
      if ds.repo.is_managed_branch():
          fr_base = DEFAULT_BRANCH
          to = DEFAULT_BRANCH
      else:
          fr_base = "HEAD"
          to = None
  
      res = _dirty_results(
          ds.diff(fr=fr_base + "~1", to=to, result_renderer="disabled")
      )
      assert_result_count(res, 1)
      assert_result_count(
          res,
          1,
          action="diff",
          path=op.join(ds.path, "new"),
          state="added",
      )
      # we can also find the diff without going through the dataset explicitly
      with chpwd(ds.path):
          assert_result_count(
              _dirty_results(
                  diff(
                      fr=fr_base + "~1",
                      to=to,
                      result_renderer="disabled",
                  )
              ),
              1,
              action="diff",
              path=op.join(ds.path, "new"),
              state="added",
          )
      # no diff against HEAD
      assert_result_count(
          _dirty_results(ds.diff(result_renderer="disabled")), 0
      )
      # modify known file
      create_tree(ds.path, {"new": "notempty"})
      res = _dirty_results(ds.diff(result_renderer="disabled"))
      assert_result_count(res, 1)
      assert_result_count(
          res,
          1,
          action="diff",
          path=op.join(ds.path, "new"),
          state="modified",
      )
      # but if we give another path, it doesn't show up
      assert_result_count(
          ds.diff(path="otherpath", result_renderer="disabled"), 0
      )
      # giving the right path must work though
      assert_result_count(
          ds.diff(path="new", result_renderer="disabled"),
          1,
          action="diff",
          path=op.join(ds.path, "new"),
          state="modified",
      )
      # stage changes
      ds.repo.add(".", git=True)
      # no change in diff, staged is not committed
      assert_result_count(
          _dirty_results(ds.diff(result_renderer="disabled")), 1
      )
      ds.save()
      assert_repo_status(ds.path)
      assert_result_count(
          _dirty_results(ds.diff(result_renderer="disabled")), 0
      )
  
      # untracked stuff
      create_tree(
          ds.path, {"deep": {"down": "untracked", "down2": "tobeadded"}}
      )
      # a plain diff should report the untracked file
      # but not directly, because the parent dir is already unknown
      res = _dirty_results(ds.diff(result_renderer="disabled"))
      assert_result_count(res, 1)
      assert_result_count(
          res,
          1,
          state="untracked",
          type="directory",
          path=op.join(ds.path, "deep"),
      )
      # report of individual files is also possible
      assert_result_count(
          ds.diff(untracked="all", result_renderer="disabled"),
          2,
          state="untracked",
          type="file",
      )
      # an unmatching path will hide this result
      assert_result_count(
          ds.diff(path="somewhere", result_renderer="disabled"), 0
      )
      # perfect match and anything underneath will do
      assert_result_count(
          ds.diff(path="deep", result_renderer="disabled"),
          1,
          state="untracked",
          path=op.join(ds.path, "deep"),
          type="directory",
      )
      assert_result_count(
          ds.diff(path="deep", result_renderer="disabled"),
          1,
          state="untracked",
          path=op.join(ds.path, "deep"),
      )
      ds.repo.add(op.join("deep", "down2"), git=True)
      # now the remaining file is the only untracked one
      assert_result_count(
          ds.diff(result_renderer="disabled"),
          1,
          state="untracked",
          path=op.join(ds.path, "deep", "down"),
          type="file",
      )
  
imports: import os
  import os.path
  from unittest.mock import patch
  import datalad.utils
  from datalad.api import create, diff, save
  from datalad.cmd import GitWitlessRunner, StdOutCapture
  from datalad.consts import PRE_INIT_COMMIT_SHA
  from datalad.distribution.dataset import Dataset
  from datalad.support.exceptions import NoDatasetFound
  from datalad.tests.utils_pytest import DEFAULT_BRANCH, OBSCURE_FILENAME, SkipTest, assert_in, assert_raises, assert_repo_status, assert_result_count, assert_status, chpwd, create_tree, eq_, get_deeply_nested_structure, has_symlink_capability, known_failure_githubci_win, neq_, ok_, with_tempfile
  from datalad.utils import Path
label_desc: Use image node_id 4 for calling a global function with example usage: test_diff(path, norepo) without return types