feat: tell libretro glue from emulator code

A libretro port carries the emulator's own sources beside its glue: pcem cites src/mem.c in the port, which is PCem's code. A citation in the port is labelled libretro glue when it is one of the libretro interface files, emulator code otherwise, and upstream emulator when it is in the original repository.

scripts/sitesources.py

@@ -120,11 +120,22 @@ def revision_markdown(profile: dict) -> str:
     return ", ".join(links)
 
 
-def role_label(profile: dict, role: str) -> str:
-    """What a reader calls the repository a role names."""
+_GLUE_RE = re.compile(r"(^|/)(libretro|retro_)[^/]*$|(^|/)libretro[^/]*/", re.IGNORECASE)
+
+
+def role_label(profile: dict, role: str, path: str = "") -> str:
+    """Whose code a cited path is, said the way a reader asks it.
+
+    A libretro port carries the emulator's own sources beside its glue: pcem
+    cites src/mem.c in the port, which is PCem's code, not the core's.
+    """
     if role == "upstream":
         return "upstream emulator"
-    return "libretro core" if "libretro" in str(profile.get("type", "")) else "this build"
+    if "libretro" not in str(profile.get("type", "")):
+        return "this build"
+    if _GLUE_RE.search(path):
+        return "libretro glue"
+    return "emulator code, libretro port"
 
 
 def role_sources(profile: dict, label: str = "") -> dict[str, tuple[upstream.Repo, str]]:
@@ -140,15 +151,17 @@ def role_sources(profile: dict, label: str = "") -> dict[str, tuple[upstream.Rep
 
 def requested_by(profile: dict, value: str | dict | None) -> str:
     """Whose code the citations of an entry are in, said in words."""
-    roles = {
-        ref_role(part.path)[0]
-        for _label, refs in source_ref_values(value)
-        for part in split_source_ref(refs)
-    } - {""}
-    if not roles or not _two_repositories(profile):
+    labels = []
+    for _label, refs in source_ref_values(value):
+        for part in split_source_ref(refs):
+            role, bare = ref_role(part.path)
+            if role:
+                label = role_label(profile, role, bare)
+                if label not in labels:
+                    labels.append(label)
+    if not labels or not _two_repositories(profile):
         return ""
-    names = [role_label(profile, role) for role in ("source", "upstream") if role in roles]
-    return " and ".join(names)
+    return labels[0] if len(labels) == 1 else ", ".join(labels[:-1]) + f" and {labels[-1]}"
 
 
 def _two_repositories(profile: dict) -> bool:
@@ -199,7 +212,7 @@ def _source_ref_markdown(profile: dict, value: str | dict | None) -> str:
                 elif len(candidates) == 1:
                     selected = candidates[0]
 
-            tag = (f" ({role_label(profile, current_role)})"
+            tag = (f" ({role_label(profile, current_role, part.path)})"
                    if current_role and _two_repositories(profile) else "")
             if selected is None:
                 rendered.append(f"`{display}`{tag}")