Set protocol.file.allow only in tests that need it

Instead of setting environment variables just on CI and for the
the entire pytest command, this has the two test cases that need
protocol.file.allow to be set to "always" (instead of "user") set
them, via a shared fixture, just while those tests are running.

Both on CI and for local test runs, this makes it no longer
necessary to set this in a global configuration or through
environment variables, reducing the setup needed to run the tests.

Author: EliahKagan

Diff for: .github/workflows/cygwin-test.yml

@@ -46,8 +46,4 @@ jobs:
       shell: bash.exe -eo pipefail -o igncr "{0}"
       run: |
         /usr/bin/python -m pytest
-      env:
-        GIT_CONFIG_COUNT: "1"
-        GIT_CONFIG_KEY_0: protocol.file.allow
-        GIT_CONFIG_VALUE_0: always
       continue-on-error: false

Diff for: .github/workflows/pythonpackage.yml

@@ -56,10 +56,6 @@ jobs:
       run: |
         set -x
         pytest
-      env:
-        GIT_CONFIG_COUNT: "1"
-        GIT_CONFIG_KEY_0: protocol.file.allow
-        GIT_CONFIG_VALUE_0: always
       continue-on-error: false
 
     - name: Documentation

Diff for: test/test_submodule.py

@@ -1,12 +1,13 @@
 # -*- coding: utf-8 -*-
 # This module is part of GitPython and is released under
 # the BSD License: http://www.opensource.org/licenses/bsd-license.php
+import contextlib
 import os
 import shutil
 import tempfile
 from pathlib import Path
 import sys
-from unittest import skipIf
+from unittest import mock, skipIf
 
 import pytest
 
@@ -31,6 +32,23 @@
 import os.path as osp
 
 
+@contextlib.contextmanager
+def _allow_file_protocol():
+    """Temporarily set protocol.file.allow to always, using environment variables."""
+    pair_index = int(os.getenv("GIT_CONFIG_COUNT", "0"))
+
+    # This is recomputed each time the context is entered, for compatibility with
+    # existing GIT_CONFIG_* environment variables, even if changed in this process.
+    patcher = mock.patch.dict(os.environ, {
+        "GIT_CONFIG_COUNT": str(pair_index + 1),
+        f"GIT_CONFIG_KEY_{pair_index}": "protocol.file.allow",
+        f"GIT_CONFIG_VALUE_{pair_index}": "always",
+    })
+
+    with patcher:
+        yield
+
+
 class TestRootProgress(RootUpdateProgress):
     """Just prints messages, for now without checking the correctness of the states"""
 
@@ -709,6 +727,7 @@ def test_add_empty_repo(self, rwdir):
         # end for each checkout mode
 
     @with_rw_directory
+    @_allow_file_protocol()
     def test_list_only_valid_submodules(self, rwdir):
         repo_path = osp.join(rwdir, "parent")
         repo = git.Repo.init(repo_path)
@@ -737,6 +756,7 @@ def test_list_only_valid_submodules(self, rwdir):
                 """,
     )
     @with_rw_directory
+    @_allow_file_protocol()
     def test_git_submodules_and_add_sm_with_new_commit(self, rwdir):
         parent = git.Repo.init(osp.join(rwdir, "parent"))
         parent.git.submodule("add", self._small_repo_url(), "module")