Fix S3 source

crates/pile-value/src/value/item.rs

@@ -40,11 +40,22 @@ impl Item {
 			Self::File { path, .. } => ItemReader::File(File::open(path)?),
 
 			Self::S3 { source, key, .. } => {
+				let full_key: SmartString<LazyCompact> = match &source.prefix {
+					None => key.clone(),
+					Some(p) => {
+						if p.ends_with('/') {
+							format!("{p}{key}").into()
+						} else {
+							format!("{p}/{key}").into()
+						}
+					}
+				};
+
 				let head = source
 					.client
 					.head_object()
 					.bucket(source.bucket.as_str())
-					.key(key.as_str())
+					.key(full_key.as_str())
 					.send()
 					.await
 					.map_err(std::io::Error::other)?;
@@ -54,7 +65,7 @@ impl Item {
 				ItemReader::S3(S3Reader {
 					client: source.client.clone(),
 					bucket: source.bucket.clone(),
-					key: key.to_owned(),
+					key: full_key,
 					cursor: 0,
 					size,
 				})