Make test helper script a file, for readability

test/fixtures/env_case.py

@@ -0,0 +1,13 @@
+import subprocess
+import sys
+
+import git
+
+
+_, working_dir, env_var_name = sys.argv
+
+# Importing git should be enough, but this really makes sure Git.execute is called.
+repo = git.Repo(working_dir)  # Hold the reference.
+git.Git(repo.working_dir).execute(["git", "version"])
+
+print(subprocess.check_output(["set", env_var_name], shell=True, text=True))

test/test_git.py

@@ -112,16 +112,12 @@ def test_it_avoids_upcasing_unrelated_environment_variable_names(self):
             raise RuntimeError("test bug or strange locale: old_name invariant under upcasing")
         os.putenv(old_name, "1")  # It has to be done this lower-level way to set it lower-case.
 
-        script_lines = [
-            "import subprocess, git",
-
-            # Importing git should be enough, but this really makes sure Git.execute is called.
-            f"repo = git.Repo({self.rorepo.working_dir!r})",
-            "git.Git(repo.working_dir).execute(['git', 'version'])",
-
-            f"print(subprocess.check_output(['set', {old_name!r}], shell=True, text=True))",
+        cmdline = [
+            sys.executable,
+            fixture_path("env_case.py"),
+            self.rorepo.working_dir,
+            old_name,
         ]
-        cmdline = [sys.executable, "-c", "\n".join(script_lines)]
         pair_text = subprocess.check_output(cmdline, shell=False, text=True)
         new_name = pair_text.split("=")[0]
         self.assertEqual(new_name, old_name)