fix: read past a blank line when attributing a ref

scripts/profile_sync.py

@@ -1136,6 +1136,9 @@ def anchor_part(
 
 SHIFT_SUPPORT = 3
 
+# Lines read past a blank cited line when scoring which repository owns it.
+BLANK_LOOKAHEAD = 5
+
 
 def dominant_shifts(
     parts: Iterable[PartResult], support: int = SHIFT_SUPPORT
@@ -1745,7 +1748,15 @@ def build_report(
                 return 2
             if start > len(lines):
                 return 0
-            line = lines[start - 1].lower()
+            # A blank cited line opens the block below it: lrps2's
+            # VMManager.cpp:418 is blank in the fork it was written for, and
+            # scored 0 it handed the ref to the upstream, where 418 is
+            # unrelated code that then decided the rebase target.
+            line = next(
+                (ln.lower() for ln in lines[start - 1:start - 1 + BLANK_LOOKAHEAD]
+                 if ln.strip()),
+                "",
+            )
             # A set name sits between delimiters in a MAME declaration, so
             # `pgm` matches `GAME( 1997, pgm,` but not `pgm_012_025_drgw2`,
             # which is what tells the two repositories apart.

tests/test_profile_sync.py

@@ -1448,6 +1448,33 @@ class TestBuildReport(unittest.TestCase):
         report = build_report("mame", profile, self.dir)
         self.assertEqual(report.entries[0].status, "ANCHORED")
 
+    def test_a_blank_first_line_does_not_hand_the_ref_to_the_upstream(self):
+        """lrps2's VMManager.cpp:418-431 opens on a blank line in the fork it
+        was written for; scored 0, the upstream (418 unrelated, not blank)
+        took the ref and its code decided the rebase target."""
+        self.files[("portpin", "src/a.cpp")] = ["x", "", "load_patches();", "y"]
+        self.files[("porthead", "src/a.cpp")] = ["", "load_patches();", "y", "w"]
+        self.files[("uppin", "src/a.cpp")] = ["x", "discord_init();", "pine();", "z"]
+        self.files[("uphead", "src/a.cpp")] = ["a", "b", "x", "discord_init();", "pine();", "z"]
+        heads = {"libretro/ps2": "porthead", "PCSX2/pcsx2": "uphead"}
+        profile_sync.upstream.resolve_head = (
+            lambda repo, cache, offline=False, branch=None: heads[repo.slug]
+        )
+        profile = {
+            "emulator": "LRPS2",
+            "source": "https://github.com/libretro/ps2",
+            "upstream": "https://github.com/PCSX2/pcsx2",
+            "source_commit": "portpin",
+            "upstream_commit": "uppin",
+            "files": [{"name": "cheats_ni.zip", "source_ref": "src/a.cpp:2-3"}],
+        }
+        report = profile_sync.report_to_dict(build_report("lrps2", profile, self.dir))
+        part = report["entries"][0]["parts"][0]
+        # Moved by -1 in the fork, the block's real target; the upstream's
+        # +2 shift of unrelated code is not it.
+        self.assertIsNone(part["repo"])
+        self.assertEqual((part["status"], part["start"]), ("SHIFTED", 1))
+
     def test_a_declared_branch_is_followed_for_head(self):
         seen = {}