add package list to Go file headers (#1474)

This allows the reader to quickly determine which versions of which packages
were used as input to the bindings generator.

Author: dicej

crates/go/src/lib.rs

@@ -15,8 +15,8 @@ use wit_bindgen_core::abi::{
 };
 use wit_bindgen_core::wit_parser::{
     Alignment, ArchitectureSize, Docs, Enum, Flags, FlagsRepr, Function, FunctionKind, Handle, Int,
-    InterfaceId, Record, Resolve, Result_, SizeAlign, Tuple, Type, TypeDefKind, TypeId, TypeOwner,
-    Variant, WorldId, WorldKey,
+    InterfaceId, Package, PackageName, Record, Resolve, Result_, SizeAlign, Tuple, Type,
+    TypeDefKind, TypeId, TypeOwner, Variant, WorldId, WorldKey,
 };
 use wit_bindgen_core::{
     AsyncFilterSet, Direction, Files, InterfaceGenerator as _, Ns, WorldGenerator, uwriteln,
@@ -776,7 +776,39 @@ impl WorldGenerator for Go {
         _ = (resolve, id);
 
         let version = env!("CARGO_PKG_VERSION");
-        let header = &format!("// Generated by `wit-bindgen` {version}. DO NOT EDIT!");
+        let packages = resolve
+            .packages
+            .iter()
+            .map(
+                |(
+                    _,
+                    Package {
+                        name:
+                            PackageName {
+                                namespace,
+                                name,
+                                version,
+                            },
+                        ..
+                    },
+                )| {
+                    let version = if let Some(version) = version {
+                        format!("@{version}")
+                    } else {
+                        String::new()
+                    };
+                    format!("//     {namespace}:{name}{version}")
+                },
+            )
+            .collect::<Vec<_>>()
+            .join("\n");
+        let header = &format!(
+            "// Generated by `wit-bindgen` {version}. DO NOT EDIT!
+//
+// This code was generated from the following packages:
+{packages}
+"
+        );
 
         let src = mem::take(&mut self.src);
         let align = self.return_area_align.format(POINTER_SIZE_EXPRESSION);