api: resolve get_url path relative to repo root

dvc/repo/__init__.py

@@ -388,8 +388,12 @@ def get_data_index_entry(
         workspace: str = "repo",
     ) -> tuple["DataIndex", "DataIndexEntry"]:
         if self.subrepos:
-            fs_path = self.dvcfs.from_os_path(path)
             fs = self.dvcfs.fs
+            fs_path = self.dvcfs.from_os_path(path)
+            # `path` is relative to the repo root, so anchor it there instead of
+            # letting it resolve against the current working directory (#11029).
+            if not fs_path.startswith(fs.root_marker):
+                fs_path = fs.join(fs.root_marker, fs_path)
             key = fs._get_key_from_relative(fs_path)
             subrepo, _, key = fs._get_subrepo_info(key)
             index = subrepo.index.data[workspace]

tests/func/api/test_data.py

@@ -32,6 +32,18 @@ def test_get_url_requires_dvc(tmp_dir, scm):
         api.get_url("foo", repo=f"file://{tmp_dir.as_posix()}")
 
 
+def test_get_url_from_subdir(tmp_dir, dvc, local_remote):
+    # `path` is documented as relative to the repo root, so the result must not
+    # depend on the current working directory (see #11029).
+    tmp_dir.dvc_gen("foo", "foo")
+    subdir = tmp_dir / "subdir"
+    subdir.mkdir()
+
+    expected = api.get_url("foo", repo=os.fspath(tmp_dir))
+    with subdir.chdir():
+        assert api.get_url("foo", repo=os.fspath(tmp_dir)) == expected
+
+
 def test_get_url_from_remote(tmp_dir, erepo_dir, cloud, local_cloud):
     erepo_dir.add_remote(config=cloud.config, name="other")
     erepo_dir.add_remote(config=local_cloud.config, default=True)