fix: finalize only the packs this run names

tests/test_finalize_pack_names.py

@@ -0,0 +1,36 @@
+"""The post-build check judges only the packs this run would name.
+
+A MiSTer _Custom pack left in the directory by a --from-md5 run was
+attached to misterfpga by substring and checked against the full list:
+0/81, FAILED, exit code 1, for a run whose own pack was 81/81.
+"""
+
+from __future__ import annotations
+
+import os
+import sys
+import tempfile
+import unittest
+import zipfile
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+
+class FinalizeByExactName(unittest.TestCase):
+    def test_a_custom_pack_is_not_judged_as_the_platform_pack(self):
+        from generate_pack import verify_and_finalize_packs
+
+        previous = os.getcwd()
+        os.chdir(REPO_ROOT)
+        self.addCleanup(os.chdir, previous)
+        with tempfile.TemporaryDirectory(dir=REPO_ROOT / "tmp") as tmp:
+            with zipfile.ZipFile(Path(tmp) / "MiSTer_FPGA_Custom_BIOS_Pack.zip", "w") as zf:
+                zf.writestr("README.txt", "custom")
+            ok = verify_and_finalize_packs(tmp, {"files": {}, "indexes": {}})
+        self.assertTrue(ok)
+
+
+if __name__ == "__main__":
+    unittest.main()