executor: fix race condition with forked git repos

When installing packages from different directories of a forked
monorepo, a race condition may occur, where multiple git clients
are interacting in parallel with the same git repository.

Fix by serializing git operations that interact with the same
git repository.

This makes the test succeed. Remove xfail.

Links:
#9658 (comment)
https://github.com/orgs/python-poetry/discussions/9718#discussioncomment-10785589

src/poetry/installation/executor.py

@@ -33,6 +33,7 @@
 from poetry.utils.helpers import remove_directory
 from poetry.utils.isolated_build import IsolatedBuildError
 from poetry.utils.isolated_build import IsolatedBuildInstallError
+from poetry.vcs.git import Git
 
 
 if TYPE_CHECKING:
@@ -46,6 +47,12 @@
     from poetry.utils.env import Env
 
 
+def _package_get_name(package: Package) -> str | None:
+    if url := package.repository_url:
+        return Git.get_name_from_source_url(url)
+    return None
+
+
 class Executor:
     def __init__(
         self,
@@ -167,8 +174,9 @@ def execute(self, operations: list[Operation]) -> int:
                 if is_parallel_unsafe:
                     serial_operations.append(operation)
                 elif operation.package.source_type == "git":
-                    # Git operations on the same repository should be executed serially
-                    serial_git_operations[operation.package.source_url].append(
+                    # Serially execute git operations that get cloned to the same directory,
+                    # to prevent multiple parallel git operations in the same repo.
+                    serial_git_operations[_package_get_name(operation.package)].append(
                         operation
                     )
                 else:
@@ -604,8 +612,6 @@ def _prepare_archive(
         )
 
     def _prepare_git_archive(self, operation: Install | Update) -> Path:
-        from poetry.vcs.git import Git
-
         package = operation.package
         assert package.source_url is not None
 

tests/installation/test_executor.py

@@ -1089,7 +1089,6 @@ def test_executor_should_install_multiple_packages_from_same_git_repository(
     assert len(spy.call_args_list) == 2
 
 
-@pytest.mark.xfail
 def test_executor_should_install_multiple_packages_from_forked_git_repository(
     mocker: MockerFixture,
     tmp_venv: VirtualEnv,