Add jobs to reproduce Cygwin safe.directory submodule issue

Remove the Cygwin xfail decorations from test_submodules in
test_docs.py and test_repo.py, and from test_root_module in
test_submodule.py, so the tests surface the underlying failure
directly.

Add 30 reproduce-safe-dir matrix jobs to cygwin-test.yml. Each runs
the three submodule tests under the current safe.directory
configuration, which covers the main repo but not submodule working
trees.

Expected result: all jobs fail. Most should fail with ValueError (git
cat-file exits due to dubious ownership, Python reads empty stdout).
A few may fail with IndexError (git cat-file exits before Python
writes to stdin, raising BrokenPipeError, which is IOError, which
iter_items catches — producing an empty submodule list).

The existing test job's env, defaults, and setup steps gain YAML
anchors so the new job can reference them without duplication.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: EliahKagan

.github/workflows/cygwin-test.yml

@@ -20,63 +20,73 @@ jobs:
 
     runs-on: windows-latest
 
-    env:
+    env: &cygwin-env
       CHERE_INVOKING: "1"
       CYGWIN_NOWINPATH: "1"
 
-    defaults:
+    defaults: &cygwin-defaults
       run:
         shell: C:\cygwin\bin\bash.exe --login --norc -eo pipefail -o igncr "{0}"
 
     steps:
-    - name: Force LF line endings
+    - &force-lf
+      name: Force LF line endings
       run: |
         git config --global core.autocrlf false  # Affects the non-Cygwin git.
       shell: pwsh  # Do this outside Cygwin, to affect actions/checkout.
 
-    - uses: actions/checkout@v6
+    - &checkout
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
 
-    - name: Install Cygwin
+    - &install-cygwin
+      name: Install Cygwin
       uses: cygwin/cygwin-install-action@v6
       with:
         packages: git python39 python-pip-wheel python-setuptools-wheel python-wheel-wheel
         add-to-path: false  # No need to change $PATH outside the Cygwin environment.
 
-    - name: Arrange for verbose output
+    - &verbose-output
+      name: Arrange for verbose output
       run: |
         # Arrange for verbose output but without shell environment setup details.
         echo 'set -x' >~/.bash_profile
 
-    - name: Special configuration for Cygwin git
+    - &safe-directory
+      name: Special configuration for Cygwin git
       run: |
         git config --global --add safe.directory "$(pwd)"
         git config --global --add safe.directory "$(pwd)/.git"
         git config --global core.autocrlf false
 
-    - name: Prepare this repo for tests
+    - &prepare-repo
+      name: Prepare this repo for tests
       run: |
         ./init-tests-after-clone.sh
 
-    - name: Set git user identity and command aliases for the tests
+    - &git-identity
+      name: Set git user identity and command aliases for the tests
       run: |
         git config --global user.email "travis@ci.com"
         git config --global user.name "Travis Runner"
         # If we rewrite the user's config by accident, we will mess it up
         # and cause subsequent tests to fail
         cat test/fixtures/.gitconfig >> ~/.gitconfig
 
-    - name: Set up virtual environment
+    - &setup-venv
+      name: Set up virtual environment
       run: |
         python3.9 -m venv .venv
         echo 'BASH_ENV=.venv/bin/activate' >>"$GITHUB_ENV"
 
-    - name: Update PyPA packages
+    - &update-pypa
+      name: Update PyPA packages
       run: |
         python -m pip install -U pip 'setuptools; python_version<"3.12"' wheel
 
-    - name: Install project and test dependencies
+    - &install-deps
+      name: Install project and test dependencies
       run: |
         pip install '.[test]'
 
@@ -91,3 +101,34 @@ jobs:
     - name: Test with pytest (${{ matrix.additional-pytest-args }})
       run: |
         pytest --color=yes -p no:sugar --instafail -vv ${{ matrix.additional-pytest-args }}
+
+  reproduce-safe-dir:
+    strategy:
+      matrix:
+        run: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30]
+      fail-fast: false
+
+    runs-on: windows-latest
+
+    env: *cygwin-env
+
+    defaults: *cygwin-defaults
+
+    steps:
+    - *force-lf
+    - *checkout
+    - *install-cygwin
+    - *verbose-output
+    - *safe-directory
+    - *prepare-repo
+    - *git-identity
+    - *setup-venv
+    - *update-pypa
+    - *install-deps
+
+    - name: Run submodule tests
+      run: |
+        python -m pytest -vv \
+          test/test_docs.py::Tutorials::test_submodules \
+          test/test_repo.py::TestRepo::test_submodules \
+          test/test_submodule.py::TestSubmodule::test_root_module

test/test_docs.py

@@ -6,9 +6,6 @@
 import gc
 import os
 import os.path
-import sys
-
-import pytest
 
 from test.lib import TestBase
 from test.lib.helper import with_rw_directory
@@ -478,11 +475,6 @@ def test_references_and_objects(self, rw_dir):
 
         repo.git.clear_cache()
 
-    @pytest.mark.xfail(
-        sys.platform == "cygwin",
-        reason="Cygwin GitPython can't find SHA for submodule",
-        raises=ValueError,
-    )
     def test_submodules(self):
         # [1-test_submodules]
         repo = self.rorepo

test/test_repo.py

@@ -877,11 +877,6 @@ def test_repo_odbtype(self):
         target_type = GitCmdObjectDB
         self.assertIsInstance(self.rorepo.odb, target_type)
 
-    @pytest.mark.xfail(
-        sys.platform == "cygwin",
-        reason="Cygwin GitPython can't find submodule SHA",
-        raises=ValueError,
-    )
     def test_submodules(self):
         self.assertEqual(len(self.rorepo.submodules), 1)  # non-recursive
         self.assertGreaterEqual(len(list(self.rorepo.iter_submodules())), 2)

test/test_submodule.py

@@ -480,11 +480,6 @@ def test_base_rw(self, rwrepo):
     def test_base_bare(self, rwrepo):
         self._do_base_tests(rwrepo)
 
-    @pytest.mark.xfail(
-        sys.platform == "cygwin",
-        reason="Cygwin GitPython can't find submodule SHA",
-        raises=ValueError,
-    )
     @pytest.mark.xfail(
         HIDE_WINDOWS_KNOWN_ERRORS,
         reason=(