Reduce to docs-only change per maintainer review

Per @Byron's feedback: dropping the is_shallow property, since a
per-commit property re-reads the shallow file on every call, which
is IO-heavy when checking many commits. Keeping just the stats()
docstring note about the limitation for a quick merge. Happy to
follow up with a Repo-level implementation (e.g. returning the set
of shallow-boundary hashes) as a separate PR if useful.

git/objects/commit.py

@@ -369,37 +369,15 @@ def iter_parents(self, paths: Union[PathLike, Sequence[PathLike]] = "", **kwargs
 
         return self.iter_items(self.repo, self, paths, **kwargs)
 
-    @property
-    def is_shallow(self) -> bool:
-        """Check whether this commit is a shallow boundary (graft) commit.
-
-        A commit at the boundary of a shallow clone appears to have no
-        parents from Git's perspective, even though the underlying commit
-        object still references a parent SHA that was never fetched. Calling
-        :attr:`stats` (or anything else that diffs against the parent) on
-        such a commit will raise :exc:`~git.exc.GitCommandError` because the
-        parent object does not exist locally.
-
-        :return:
-            True if this commit's hexsha appears in the repository's
-            ``shallow`` file, False otherwise (including for non-shallow
-            repositories).
-        """
-        shallow_file = os.path.join(self.repo.git_dir, "shallow")
-        if not os.path.isfile(shallow_file):
-            return False
-        with open(shallow_file, "r") as f:
-            return self.hexsha in f.read().split()
-
     @property
     def stats(self) -> Stats:
         """Create a git stat from changes between this commit and its first parent
         or from all changes done if this is the very first commit.
 
         :note:
-            If this commit is at the boundary of a shallow clone (see
-            :attr:`is_shallow`), this will raise :exc:`~git.exc.GitCommandError`
-            because the parent object was never fetched.
+            If this commit is at the boundary of a shallow clone, this will
+            raise :exc:`~git.exc.GitCommandError`, since the parent object
+            was never fetched and only exists as a reference on this commit.
 
         :return:
             :class:`Stats`

test/test_commit.py

@@ -164,25 +164,6 @@ def check_entries(d, has_change_type=False):
         self.assertEqual(commit.committer_tz_offset, 14400, commit.committer_tz_offset)
         self.assertEqual(commit.message, "initial project\n")
 
-    @with_rw_directory
-    def test_is_shallow(self, rw_dir):
-        """A commit at the shallow boundary should report is_shallow, and
-        accessing its stats should raise GitCommandError."""
-        full_repo = self.rorepo
-        shallow_path = osp.join(rw_dir, "shallow_clone")
-        shallow_repo = Repo.clone_from(full_repo.git_dir, shallow_path, depth=2, no_local=True)
-
-        commits = list(shallow_repo.iter_commits())
-        boundary_commit = commits[-1]
-
-        self.assertTrue(boundary_commit.is_shallow)
-        with self.assertRaises(GitCommandError):
-            boundary_commit.stats
-
-        if len(commits) > 1:
-            non_boundary_commit = commits[0]
-            self.assertFalse(non_boundary_commit.is_shallow)
-
     def test_renames(self):
         commit = self.rorepo.commit("185d847ec7647fd2642a82d9205fb3d07ea71715")
         files = commit.stats.files