WIP - Support selecting an operation inside a query document

See issue #31 for a discussion of the feature.

We should document this at some point, probably not in the README or it is going to get cluttered.

Author: tomhoule

graphql_query_derive/src/codegen.rs

@@ -10,6 +10,7 @@ use selection::Selection;
 pub(crate) fn response_for_query(
     schema: schema::Schema,
     query: query::Document,
+    selected_operation: Option<String>,
 ) -> Result<TokenStream, failure::Error> {
     let mut context = QueryContext::new(schema);
     let mut definitions = Vec::new();