config: don't look for .dvc dir implicitly

Currently if dvc_dir doesn't exists (e.g. we are creating an uninitialized
repo), config will try looking for `.dvc` dir in the current directory,
which might be inside of another dvc repository resulting in mixed configs.

Use explicit `from_cwd` method to make `Config` try to find repo configs
if available to avoid the usage mixup.

tests/func/test_config.py

@@ -245,7 +245,7 @@ def test_merging_two_levels(dvc):
 
 def test_config_loads_without_error_for_non_dvc_repo(tmp_dir):
     # regression testing for https://github.com/iterative/dvc/issues/3328
-    Config(validate=True)
+    Config.from_cwd(validate=True)
 
 
 @pytest.mark.parametrize(
@@ -284,7 +284,7 @@ def test_config_gdrive_fields(tmp_dir, dvc):
             "profile": "myprofile",
         }
 
-    Config(validate=True)
+    Config.from_cwd(validate=True)
 
 
 def test_config_remote(tmp_dir, dvc, capsys):

tests/unit/test_config.py

@@ -25,7 +25,7 @@ def test_get_fs(tmp_dir, scm):
     tmp_dir.scm_gen("foo", "foo", commit="add foo")
 
     fs = scm.get_fs("master")
-    config = Config(fs=fs)
+    config = Config.from_cwd(fs=fs)
 
     assert config.fs == fs
     assert config.wfs != fs
@@ -38,7 +38,7 @@ def test_get_fs(tmp_dir, scm):
 
 
 def test_s3_ssl_verify(tmp_dir, dvc):
-    config = Config(validate=False)
+    config = Config.from_cwd(validate=False)
     with config.edit() as conf:
         conf["remote"]["remote-name"] = {"url": "s3://bucket/dvc"}
 
@@ -74,7 +74,7 @@ def test_s3_ssl_verify(tmp_dir, dvc):
 
 
 def test_load_unicode_error(tmp_dir, dvc, mocker):
-    config = Config(validate=False)
+    config = Config.from_cwd(validate=False)
     mocker.patch(
         "configobj.ConfigObj",
         side_effect=UnicodeDecodeError("", b"", 0, 0, ""),
@@ -87,7 +87,7 @@ def test_load_unicode_error(tmp_dir, dvc, mocker):
 def test_load_configob_error(tmp_dir, dvc, mocker):
     from configobj import ConfigObjError
 
-    config = Config(validate=False)
+    config = Config.from_cwd(validate=False)
     mocker.patch(
         "configobj.ConfigObj",
         side_effect=ConfigObjError(),