refactor: DRY consolidation + 83 unit tests

Moved shared functions to common.py (single source of truth):
- check_inside_zip (was in verify.py, imported by generate_pack)
- build_zip_contents_index (was duplicated in verify + generate_pack)
- load_emulator_profiles (was in verify, cross_reference, generate_site)
- group_identical_platforms (was in verify + generate_pack)

Added tests/ with 83 unit tests covering:
- resolve_local_file: SHA1, MD5, name, alias, truncated, zip_contents
- verify: existence, md5, zipped_file, multi-hash, severity mapping
- aliases: field parsing, by_name indexing, beetle_psx field rename
- pack: dedup, file_status, zipped_file inner check, EmuDeck entries
- severity: all 12 combinations, platform-native behavior

0 regressions: pipeline.py --all produces identical results.

tests/test_aliases.py

@@ -0,0 +1,201 @@
+"""Tests for alias support in resolve_local_file and generate_db."""
+
+from __future__ import annotations
+
+import os
+import sys
+import tempfile
+import unittest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "scripts"))
+from common import compute_hashes, resolve_local_file
+from generate_db import build_indexes
+
+
+class TestAliasesInResolve(unittest.TestCase):
+    """Test that aliases field in file_entry enables resolution."""
+
+    def setUp(self):
+        self.tmpdir = tempfile.mkdtemp()
+        self.content = b"colecovision bios content"
+        self.file_path = os.path.join(self.tmpdir, "colecovision.rom")
+        with open(self.file_path, "wb") as f:
+            f.write(self.content)
+        hashes = compute_hashes(self.file_path)
+        self.sha1 = hashes["sha1"]
+        self.md5 = hashes["md5"]
+
+        self.db = {
+            "files": {
+                self.sha1: {
+                    "path": self.file_path,
+                    "name": "colecovision.rom",
+                    "md5": self.md5,
+                    "size": len(self.content),
+                },
+            },
+            "indexes": {
+                "by_md5": {self.md5: self.sha1},
+                "by_name": {
+                    "colecovision.rom": [self.sha1],
+                    "coleco.rom": [self.sha1],
+                },
+                "by_crc32": {},
+            },
+        }
+
+    def tearDown(self):
+        import shutil
+        shutil.rmtree(self.tmpdir, ignore_errors=True)
+
+    def test_aliases_field_enables_name_resolution(self):
+        """file_entry with aliases: names_to_try includes aliases."""
+        entry = {
+            "name": "BIOS.col",
+            "aliases": ["coleco.rom"],
+        }
+        path, status = resolve_local_file(entry, self.db)
+        self.assertIsNotNone(path)
+        self.assertEqual(path, self.file_path)
+
+    def test_primary_name_tried_first(self):
+        entry = {
+            "name": "colecovision.rom",
+            "aliases": ["coleco.rom"],
+        }
+        path, status = resolve_local_file(entry, self.db)
+        self.assertEqual(status, "exact")
+        self.assertEqual(path, self.file_path)
+
+    def test_alias_duplicate_of_name_ignored(self):
+        """If alias == name, it's not added twice to names_to_try."""
+        entry = {
+            "name": "colecovision.rom",
+            "aliases": ["colecovision.rom"],
+        }
+        path, status = resolve_local_file(entry, self.db)
+        self.assertEqual(status, "exact")
+
+
+class TestBuildIndexesWithAliases(unittest.TestCase):
+    """Test that build_indexes merges alias names into by_name."""
+
+    def test_aliases_indexed_in_by_name(self):
+        files = {
+            "sha1abc": {
+                "name": "gb_bios.bin",
+                "md5": "md5abc",
+                "crc32": "crc32abc",
+            },
+        }
+        aliases = {
+            "sha1abc": [
+                {"name": "dmg_boot.bin", "path": ""},
+                {"name": "dmg_rom.bin", "path": ""},
+            ],
+        }
+        indexes = build_indexes(files, aliases)
+        self.assertIn("gb_bios.bin", indexes["by_name"])
+        self.assertIn("dmg_boot.bin", indexes["by_name"])
+        self.assertIn("dmg_rom.bin", indexes["by_name"])
+        self.assertEqual(indexes["by_name"]["dmg_boot.bin"], ["sha1abc"])
+        self.assertEqual(indexes["by_name"]["gb_bios.bin"], ["sha1abc"])
+
+    def test_alias_not_duplicated(self):
+        """Same SHA1 not added twice for same alias name."""
+        files = {
+            "sha1abc": {
+                "name": "gb_bios.bin",
+                "md5": "md5abc",
+                "crc32": "crc32abc",
+            },
+        }
+        aliases = {
+            "sha1abc": [
+                {"name": "dmg_boot.bin", "path": ""},
+                {"name": "dmg_boot.bin", "path": "other/path"},
+            ],
+        }
+        indexes = build_indexes(files, aliases)
+        # SHA1 should appear only once
+        self.assertEqual(indexes["by_name"]["dmg_boot.bin"].count("sha1abc"), 1)
+
+
+class TestKnownAliasGroups(unittest.TestCase):
+    """Test that KNOWN_ALIAS_GROUPS cross-linking works via build_indexes."""
+
+    def test_known_alias_groups_structure(self):
+        """Verify KNOWN_ALIAS_GROUPS is a list of lists of strings."""
+        from generate_db import _collect_all_aliases
+        # We can't easily call _collect_all_aliases without the real repo,
+        # but we can verify the constant exists and has the right structure.
+        # Import the source to check the constant inline.
+        import importlib
+        import generate_db
+        with open(generate_db.__file__) as fh:
+            source = fh.read()
+        self.assertIn("KNOWN_ALIAS_GROUPS", source)
+        self.assertIn("colecovision.rom", source)
+        self.assertIn("coleco.rom", source)
+        self.assertIn("gb_bios.bin", source)
+        self.assertIn("dmg_boot.bin", source)
+
+
+class TestBeetlePsxAliasField(unittest.TestCase):
+    """Verify aliases field (renamed from alt_names) is used in resolution."""
+
+    def setUp(self):
+        self.tmpdir = tempfile.mkdtemp()
+        self.content = b"psx bios"
+        self.file_path = os.path.join(self.tmpdir, "scph5501.bin")
+        with open(self.file_path, "wb") as f:
+            f.write(self.content)
+        hashes = compute_hashes(self.file_path)
+        self.sha1 = hashes["sha1"]
+        self.md5 = hashes["md5"]
+
+        self.db = {
+            "files": {
+                self.sha1: {
+                    "path": self.file_path,
+                    "name": "scph5501.bin",
+                    "md5": self.md5,
+                    "size": len(self.content),
+                },
+            },
+            "indexes": {
+                "by_md5": {self.md5: self.sha1},
+                "by_name": {
+                    "scph5501.bin": [self.sha1],
+                    "ps-22a.bin": [self.sha1],
+                },
+                "by_crc32": {},
+            },
+        }
+
+    def tearDown(self):
+        import shutil
+        shutil.rmtree(self.tmpdir, ignore_errors=True)
+
+    def test_aliases_field_not_alt_names(self):
+        """The field is 'aliases', not 'alt_names'."""
+        entry = {
+            "name": "ps-22a.bin",
+            "aliases": ["scph5501.bin"],
+        }
+        path, status = resolve_local_file(entry, self.db)
+        self.assertIsNotNone(path)
+
+    def test_alt_names_field_ignored(self):
+        """'alt_names' field is not recognized, only 'aliases'."""
+        entry = {
+            "name": "nonexistent.bin",
+            "alt_names": ["scph5501.bin"],
+        }
+        path, status = resolve_local_file(entry, self.db)
+        self.assertIsNone(path)
+        self.assertEqual(status, "not_found")
+
+
+if __name__ == "__main__":
+    unittest.main()