Add branch CLI command and tests (see ChatGPT conversation: https://chatgpt.com/share/69370ce1-8090-800f-8b08-8ecfa5089a74)

Signed-off-by: Kevin Veen-Birkenbach <kevin@veen.world>

tests/e2e/test_integration_branch_commands.py

@@ -0,0 +1,63 @@
+from __future__ import annotations
+
+import runpy
+import sys
+import unittest
+from unittest.mock import patch
+
+
+class TestIntegrationBranchCommands(unittest.TestCase):
+    """
+    E2E-style tests for the 'pkgmgr branch' CLI wiring.
+
+    We do NOT call real git; instead we patch pkgmgr.branch_commands.open_branch
+    and verify that the CLI invokes it with the correct parameters.
+    """
+
+    def _run_pkgmgr(self, argv: list[str]) -> None:
+        """
+        Helper to run 'pkgmgr' via its entry module with a given argv.
+        """
+        original_argv = list(sys.argv)
+        try:
+            # argv typically looks like: ["pkgmgr", "branch", ...]
+            sys.argv = argv
+            # Run the CLI entry point
+            runpy.run_module("pkgmgr.cli", run_name="__main__")
+        finally:
+            sys.argv = original_argv
+
+    @patch("pkgmgr.branch_commands.open_branch")
+    def test_branch_open_with_name_and_base(self, mock_open_branch) -> None:
+        """
+        pkgmgr branch open feature/test --base develop
+        should invoke open_branch(name='feature/test', base_branch='develop', cwd='.')
+        """
+        self._run_pkgmgr(
+            ["pkgmgr", "branch", "open", "feature/test", "--base", "develop"]
+        )
+
+        mock_open_branch.assert_called_once()
+        _, kwargs = mock_open_branch.call_args
+        self.assertEqual(kwargs.get("name"), "feature/test")
+        self.assertEqual(kwargs.get("base_branch"), "develop")
+        self.assertEqual(kwargs.get("cwd"), ".")
+
+    @patch("pkgmgr.branch_commands.open_branch")
+    def test_branch_open_without_name_uses_default_base(self, mock_open_branch) -> None:
+        """
+        pkgmgr branch open
+        should invoke open_branch(name=None, base_branch='main', cwd='.')
+        (the branch name will be asked interactively inside open_branch).
+        """
+        self._run_pkgmgr(["pkgmgr", "branch", "open"])
+
+        mock_open_branch.assert_called_once()
+        _, kwargs = mock_open_branch.call_args
+        self.assertIsNone(kwargs.get("name"))
+        self.assertEqual(kwargs.get("base_branch"), "main")
+        self.assertEqual(kwargs.get("cwd"), ".")
+
+
+if __name__ == "__main__":
+    unittest.main()