CI is broken for convert_to_parquet: Invalid rev id: refs/pr/1 404 error causes RevisionNotFoundError

See: https://github.com/huggingface/datasets/actions/runs/10095313567/job/27915185756
```
FAILED tests/test_hub.py::test_convert_to_parquet - huggingface_hub.utils._errors.RevisionNotFoundError: 404 Client Error. (Request ID: Root=1-66a25839-31ce7b475e70e7db1e4d44c2;b0c8870f-d5ef-4bf2-a6ff-0191f3df0f64)

Revision Not Found for url: https://hub-ci.huggingface.co/api/datasets/__DUMMY_TRANSFORMERS_USER__/test-dataset-5188a8-17219154347516/preupload/refs%2Fpr%2F1.
Invalid rev id: refs/pr/1
```
```
 /opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/datasets/hub.py:86: in convert_to_parquet
    dataset.push_to_hub(
/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/datasets/dataset_dict.py:1722: in push_to_hub
    split_additions, uploaded_size, dataset_nbytes = self[split]._push_parquet_shards_to_hub(
/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/datasets/arrow_dataset.py:5511: in _push_parquet_shards_to_hub
    api.preupload_lfs_files(
/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/huggingface_hub/hf_api.py:4231: in preupload_lfs_files
    _fetch_upload_modes(
/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/huggingface_hub/utils/_validators.py:118: in _inner_fn
    return fn(*args, **kwargs)
/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/huggingface_hub/_commit_api.py:507: in _fetch_upload_modes
    hf_raise_for_status(resp)
```

Any recent change in the API backend rejecting parameter `revision="refs/pr/1"` to `HfApi.preupload_lfs_files`?
```
f"{endpoint}/api/{repo_type}s/{repo_id}/preupload/{revision}"

https://hub-ci.huggingface.co/api/datasets/__DUMMY_TRANSFORMERS_USER__/test-dataset-5188a8-17219154347516/preupload/refs%2Fpr%2F1.
Invalid rev id: refs/pr/1
```
@Wauplin  @huggingface/datasets @huggingface/moon-landing @huggingface/moon-landing-back 

I have temporarily fixed the CI with:
- #7074

However, the underlying issue must be fixed and #7074 must be reverted.

Hmm does it do the preupload call before creating the ref cc @Wauplin ?

(in that case it should do a preupload call on the base branch with `?create_pr=1`)

@coyotte508, the CI test was implemented 2 months ago and it was working OK until yesterday. See the CI status of the commits in the main branch of `datasets`: https://github.com/huggingface/datasets/commits/main/

Yes i get that

We changed the preupload response to return the commit id in https://github.com/huggingface-internal/moon-landing/pull/10756

This line is probably causing the error: https://github.com/huggingface-internal/moon-landing/pull/10756/files#diff-558f6f9865e30bfa091b94d6a4a900138103ddb4eb0bec96b6deec5bf5626fa0R2322

It's weird the error is returned, it means that maybe a ref with 0 history (not even the first commit) was created

Does this change have any impact in production, or just the CI test? If it's just the CI test it should be fixed on your side, if it impacts production we can look at a solution

@coyotte508 it impacts production: `convert_to_parquet` raises the above error when the dataset has more that one configs/subsets:
- First subset calls `push_to_hub` with `create_pr=True`
- Second subset uses the `refs/pr/#` returned by the call above, and calls `push_to_hub` with `revision="refs/pr/#"`

I tried removing the `mock_commit` call: https://github.com/huggingface/datasets/pull/7076

And the tests seem to work.

So it's probably because the commit is not actually called, it doesn't actually create the pull request on the remote (and the associated `refs/pr/1`). But the `preupload` call is not mocked.

Anyway it shouldn't impact production, since production isn't mocked

@coyotte508 thanks a lot for the investigation and sorry for the noise. 
I promise not trying to fix things when I have a slight fever: my head does not work well.

We need indeed to mock `preupload_lfs_files`: before it was not necessary, but now it is.

I fixed the test in:
- #7078

Thanks again, @coyotte508.