feat: pack readme names spellings left out

A pack folded for Windows and macOS keeps one spelling of each case twin. Extracted on a Steam Deck or Linux, the core asking for the other spelling finds nothing, and only the installer added it. Where the platform also runs on a filesystem that keeps case, the README now lists each spelling left out beside the one it holds: 12 for EmuDeck and 10 for RetroArch, the manifest's case_variants.

tests/test_case_insensitive_platforms.py

@@ -7,7 +7,12 @@ went red. The flag lived in retrobat.yml and vanished at the next scrape.
 
 from __future__ import annotations
 
+import contextlib
+import hashlib
+import io
+import os
 import sys
+import tempfile
 import unittest
 from pathlib import Path
 
@@ -29,5 +34,82 @@ class CaseInsensitiveWhereTheFilesystemIs(unittest.TestCase):
                     self.assertTrue(config.get("case_insensitive_fs"))
 
 
+class ThePackReadmeNamesTheSpellingsItLeavesOut(unittest.TestCase):
+    """The EmuDeck pack is folded for Windows and extracted on a Steam Deck,
+    where the core asking for bios.col finds only BIOS.col. Only the
+    installer adds that spelling (case_variants), and the pack's README said
+    nothing about it."""
+
+    def setUp(self):
+        import common
+        import generate_db
+        import generate_pack
+
+        self.gp = generate_pack
+        tmp = tempfile.TemporaryDirectory(dir=REPO_ROOT / "tmp")
+        self.addCleanup(tmp.cleanup)
+        previous = os.getcwd()
+        os.chdir(tmp.name)
+        self.addCleanup(os.chdir, previous)
+        Path("bios/Coleco").mkdir(parents=True)
+        payload = b"coleco bios"
+        Path("bios/Coleco/BIOS.col").write_bytes(payload)
+        sha1 = hashlib.sha1(payload).hexdigest()
+        files = {sha1: {"path": "bios/Coleco/BIOS.col", "name": "BIOS.col",
+                        "size": len(payload), "sha1": sha1,
+                        "md5": hashlib.md5(payload).hexdigest(),
+                        "sha256": hashlib.sha256(payload).hexdigest(),
+                        "crc32": "00000001"}}
+        self.db = {"files": files, "indexes": generate_db.build_indexes(files, {})}
+        Path("platforms").mkdir()
+        Path("emulators").mkdir()
+        self.config = {
+            "platform": "P", "verification_mode": "existence",
+            "case_insensitive_fs": True, "cores": ["mesence"],
+            "systems": {"coleco": {"files": [{"name": "BIOS.col"}]}},
+        }
+        Path("emulators/mesence.yml").write_text(yaml.dump({
+            "emulator": "mesence", "type": "libretro", "systems": ["coleco"],
+            "files": [{"name": "bios.col", "required": True}],
+        }))
+        common._platform_config_cache.clear()
+        common._emulator_profiles_cache.clear()
+        self.addCleanup(common._platform_config_cache.clear)
+        self.addCleanup(common._emulator_profiles_cache.clear)
+
+    def _readme(self, systems: list[str]) -> str:
+        import common
+
+        Path("platforms/p.yml").write_text(yaml.dump(self.config))
+        Path("platforms/_registry.yml").write_text(yaml.dump({"platforms": {"p": {
+            "status": "active",
+            "install": {"detect": [{"os": os_name} for os_name in systems]},
+        }}}))
+        common._platform_config_cache.clear()
+        texts: dict[str, str] = {}
+        real = self.gp._write_generated_member
+
+        def capture(zf, arcname, text):
+            texts[arcname] = text
+            return real(zf, arcname, text)
+
+        self.gp._write_generated_member = capture
+        self.addCleanup(setattr, self.gp, "_write_generated_member", real)
+        with contextlib.redirect_stdout(io.StringIO()):
+            self.gp.generate_pack(
+                "p", "platforms", self.db, "bios", "", emulators_dir="emulators",
+                offline=True, record=self.gp.PackRecord(),
+            )
+        return texts["README.txt"]
+
+    def test_a_platform_also_on_linux_names_them(self):
+        readme = self._readme(["windows", "linux"])
+        self.assertIn("NAMES THAT DIFFER ONLY BY CASE", readme)
+        self.assertIn("    bios.col  (the pack has BIOS.col)", readme)
+
+    def test_a_platform_only_on_windows_does_not(self):
+        self.assertNotIn("DIFFER ONLY BY CASE", self._readme(["windows"]))
+
+
 if __name__ == "__main__":
     unittest.main()