When trying to publish to pypi, we get:
```
Invalid value for requires_dist. Error: Can't have direct dependency:
"gdrivefs @ git+https://github.com/intake/gdrivefs.git ; extra ==
'tests'"
```
Some of the tests are run by default, other requires
`--enable-{remote}` to run. The remotes that are run by default
also have a `--disable-{remote}` flag. All of the remotes can be
enabled using `--all` flag.
To use this functionality in the fixture,
`test_config` fixture has to be used, and requires to call
`test_config.requires(remote)`.
In an individual test, you can simply use `pytest.mark.remote`
to make them skip or run.
* dvc: get rid of is_walking_tree
No longer needed. Some applications of `isinstance()` will be refactored
in the future, as trees will just provide the needed functionality.
* dvc: move GitTree to dvc/tree/
* dvc: rename *RemoteTree to *Tree
Usually we need it to parametrize tests with, so there is no
reason to duplicate the code. I've left `local_remote` fixture
just because it is so convenient and often used in a lot of tests.
Batuhan Taskaya
Ruslan Kuprieiev
Saugat Pachhai