fix: kernels upload to a repo branch

src/kernels/cli.py

@@ -4,7 +4,7 @@
 import sys
 from pathlib import Path
 
-from huggingface_hub import create_repo, upload_folder
+from huggingface_hub import create_repo, upload_folder, create_branch
 
 from kernels.compat import tomllib
 from kernels.lockfile import KernelLock, get_kernel_locks
@@ -204,6 +204,7 @@ def lock_kernels(args):
 
 
 def upload_kernels(args):
+    # Resolve `kernel_dir` to be uploaded.
     kernel_dir = Path(args.kernel_dir).resolve()
     build_dir = kernel_dir / "build"
     if not kernel_dir.is_dir():
@@ -215,6 +216,9 @@ def upload_kernels(args):
         repo_id=args.repo_id, private=args.private, exist_ok=True
     ).repo_id
 
+    if args.branch is not None:
+        create_branch(repo_id=repo_id, branch=args.branch, exist_ok=True)
+
     delete_patterns: set[str] = set()
     for build_variant in build_dir.iterdir():
         if build_variant.is_dir():

tests/test_kernel_upload.py

@@ -7,7 +7,7 @@
 from typing import List
 
 import pytest
-from huggingface_hub import delete_repo, model_info
+from huggingface_hub import delete_repo, model_info, list_repo_refs
 
 from kernels.cli import upload_kernels
 
@@ -83,6 +83,11 @@ def test_kernel_upload_works_as_expected(branch):
 
     repo_filenames = get_filenames_from_a_repo(REPO_ID)
     assert any(str(script_path.name) for f in repo_filenames)
+
+    if branch is not None:
+        refs = list_repo_refs(repo_id=REPO_ID)
+        assert any(ref_branch.name == branch for ref_branch in refs.branches)
+
     delete_repo(repo_id=REPO_ID)
 
 
@@ -95,7 +100,7 @@ def test_kernel_upload_deletes_as_expected():
         build_dir.mkdir(parents=True, exist_ok=True)
         script_path = build_dir / "foo_2025.py"
         script_path.write_text(PY_CONTENT)
-        upload_kernels(UploadArgs(tmpdir, REPO_ID, False))
+        upload_kernels(UploadArgs(tmpdir, REPO_ID, False, None))
 
     repo_filenames = get_filenames_from_a_repo(REPO_ID)
     filename_to_change = get_filename_to_change(repo_filenames)
@@ -107,7 +112,7 @@ def test_kernel_upload_deletes_as_expected():
         changed_filename = next_filename(Path(filename_to_change))
         script_path = build_dir / changed_filename
         script_path.write_text(PY_CONTENT)
-        upload_kernels(UploadArgs(tmpdir, REPO_ID, False))
+        upload_kernels(UploadArgs(tmpdir, REPO_ID, False, None))
 
     repo_filenames = get_filenames_from_a_repo(REPO_ID)
     assert any(str(changed_filename) in k for k in repo_filenames), f"{repo_filenames=}"