feat: say why an upstream revision is held

The emulator page showed the reason for pin_frozen and never the one for upstream_frozen, which 11 profiles record: mupen64plus read as left behind HEAD.

scripts/generate_site.py

@@ -7984,10 +7984,14 @@ def _build_rows(profile: dict) -> list[str]:
     found = _found_by_text(profile.get("found_by"))
     if found:
         rows.append(f"| Files found by | {found} |")
-    frozen = profile.get("pin_frozen")
-    if frozen:
-        held = _escape_tags(' '.join(str(frozen).split())).replace('|', r'\|')
-        rows.append(f"| Revision held | {held} |")
+    # Each pin says why it is held: a bare upstream revision read as a
+    # profile left behind HEAD (mupen64plus, aps3e).
+    for field, label in (("pin_frozen", "Revision held"),
+                         ("upstream_frozen", "Upstream revision held")):
+        frozen = profile.get(field)
+        if frozen:
+            held = _escape_tags(' '.join(str(frozen).split())).replace('|', r'\|')
+            rows.append(f"| {label} | {held} |")
     announced = profile.get("version_source")
     if isinstance(announced, dict) and announced.get("url"):
         url = str(announced["url"])

tests/test_site_emulator_page.py

@@ -68,6 +68,17 @@ class WhoShipsTheBuildAndWhy(unittest.TestCase):
                       "(https://example.org/news) (version 13.0 announced there, "
                       "found only as rebuilt copies) |", page)
 
+    def test_the_upstream_pin_says_why_it_is_held(self):
+        """mupen64plus showed its core revision and not that AmberELEC
+        builds that one: read as a profile behind HEAD."""
+        page = _page("mupen64plus", {
+            "type": "libretro",
+            "upstream_frozen": "AmberELEC builds the core at this revision.",
+            "files": [],
+        })
+        self.assertIn("| Upstream revision held | AmberELEC builds the core at this "
+                      "revision. |", page)
+
 
 class ACardKeepsItsAddress(unittest.TestCase):
     """emulators/raze/#file-duke3d-grp stopped pointing at its card once a