update-shape.py apply --branch prints the root's own tracking branch as the gh pr create --base and its assembly repository as the --repo, the two values --pr passes, so a project scaffolded with --tracking-branch trunk is no longer told to open its pull request against main, and the --push line no longer prints a literal <org>/<Project> that a shell reads as a redirection (#209)

tests/test_update_shape.py

@@ -78,14 +78,19 @@ def update_shape():
 MAKEFILE_SOURCE = f"templates/assembly-root/{MAKEFILE}"
 
 
-def scaffold_upstream_and_project(tmp_path_factory, subdir: str):
+def scaffold_upstream_and_project(tmp_path_factory, subdir: str,
+                                  *scaffold_args: str):
     """A fresh clone of this repository at A, and `PROJECT` scaffolded from
     it into a recursive clone of its own — the part `upstream_and_project`
     and `adopted_upstream_and_project` share verbatim. They differ only in
     what commits they make on top afterward, which is why this stops here
     and returns the pieces rather than a finished fixture dict: a shared
     RETURN SHAPE across two fixtures is how the second one quietly drifts
     from the first.
+
+    `scaffold_args` are extra flags for `scaffold-project.py` — a
+    `--tracking-branch`, for the project whose pull requests must not be
+    told to land on `main` (#209).
     """
     base = tmp_path_factory.mktemp(subdir)
     upstream = base / "openRepoShape"
@@ -98,7 +103,7 @@ def scaffold_upstream_and_project(tmp_path_factory, subdir: str):
         upstream / "scaffold-project.py", "--org", ORG, "--project", PROJECT,
         "--elected-by", "Test Human", "--elected-on", "2026-09-02",
         "--local-remote-dir", str(base / "remotes"),
-        "--work-dir", str(base / "work"))
+        "--work-dir", str(base / "work"), *scaffold_args)
     assert result.returncode == 0, result.stderr + result.stdout
 
     clone = base / "clone" / PROJECT