[PATCH b4] tests: pin scratch repos to master regardless of init.defaultBranch

[Hangbin Liu <hangbin.liu@linux.dev>]

From: Hangbin Liu <liuhangbin@kylinos.cn>

_init_repo() ran a plain "git init", so the scratch repo's initial
branch followed the developer's init.defaultBranch. On a machine
configured with init.defaultBranch=main (increasingly the norm), the
repos come up on main, and test_base_commit_in_remote_tree then fails
at its "git checkout master".

Pins -b master on the local side so the suite passes regardless of the
developer's default-branch configuration.

Assisted-by: LLM [analysis, codegen]
Fixes: 4ee47be995f2 ("ty: verify queued-thanks commits by ref reachability, not HTTP status")
Signed-off-by: Hangbin Liu <liuhangbin@kylinos.cn>
---
 src/tests/test_ty.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/tests/test_ty.py b/src/tests/test_ty.py
index 269ce021306f..2901f053f0f5 100644
--- a/src/tests/test_ty.py
+++ b/src/tests/test_ty.py
@@ -401,7 +401,9 @@ def test_get_check_repo_config_override(monkeypatch: pytest.MonkeyPatch) -> None
 
 
 def _init_repo(path: str) -> None:
-    ecode, out = b4.git_run_command(None, ['init', path])
+    # -b master: some tests check out "master" by name, and an
+    # init.defaultBranch of 'main' would leave no such branch to find.
+    ecode, out = b4.git_run_command(None, ['init', '-b', 'master', path])
     assert ecode == 0, out
     b4.git_set_config(path, 'user.name', 'Test')
     b4.git_set_config(path, 'user.email', 'test@example.com')

---
base-commit: 6be7c6139d7734d84afddf989fa2874935b6d85b
change-id: 20261020-test_base_commit-d258e41c094a

Best regards,
--  
Hangbin Liu <liuhangbin@kylinos.cn>