fix: handle unborn HEAD branch creation

- Create orphan branches when HEAD does not exist yet\n- Use current branch as the default branch base in the toolbar\n- Keep push disabled for remote-less repos\n\nQuality gates: vitest repositories-settings-tab (passed); api pytest blocked by missing fastapi in environment

apps/api/tests/unit/test_git_repository_working_clones.py

@@ -4,6 +4,7 @@ import pytest
 from fastapi import HTTPException
 
 from src.api.git_repositories import _clone_working_repository, _init_working_repository
+from src.utils.git_control import create_branch
 
 
 def test_clone_working_repository_uses_normal_clone() -> None:
@@ -44,3 +45,14 @@ def test_init_working_repository_falls_back_to_symbolic_ref() -> None:
     assert run_mock.call_args_list[0].args[0] == ["git", "init", "-b", "main", "/tmp/new-repo"]
     assert run_mock.call_args_list[1].args[0] == ["git", "init", "/tmp/new-repo"]
     assert run_mock.call_args_list[2].args[0] == ["git", "-C", "/tmp/new-repo", "symbolic-ref", "HEAD", "refs/heads/main"]
+
+
+def test_create_branch_uses_orphan_checkout_when_head_is_unborn() -> None:
+    verify_head = Mock(returncode=128, stderr="fatal: Needed a single revision")
+    checkout_orphan = Mock(returncode=0, stderr="")
+
+    with patch("src.utils.git_control._run_git_command", side_effect=[verify_head, checkout_orphan]) as run_mock:
+        create_branch("/tmp/new-repo", "feature/test")
+
+    assert run_mock.call_args_list[0].args[1:] == ("rev-parse", "--verify", "HEAD")
+    assert run_mock.call_args_list[1].args[1:] == ("checkout", "--orphan", "feature/test")