to be squashed: use itertools for formatting

Author: fnune

graphql_client_codegen/Cargo.toml

@@ -8,6 +8,7 @@ repository = "https://github.com/graphql-rust/graphql-client"
 
 [dependencies]
 failure = "0.1"
+itertools = "0.8"
 lazy_static = "1.0"
 quote = "0.6"
 syn = "0.15.20"

graphql_client_codegen/src/lib.rs

@@ -9,6 +9,7 @@
 extern crate failure;
 extern crate graphql_parser;
 extern crate heck;
+extern crate itertools;
 #[macro_use]
 extern crate lazy_static;
 extern crate proc_macro;

graphql_client_codegen/src/shared.rs

@@ -5,18 +5,10 @@ use objects::GqlObjectField;
 use proc_macro2::{Ident, Span, TokenStream};
 use query::QueryContext;
 use selection::*;
+use itertools::Itertools;
 
 fn format_available_fields(fields: &[GqlObjectField]) -> String {
-    fields
-        .iter()
-        .map(|ref field| &field.name)
-        .fold(String::new(), |mut acc, item| {
-            acc.push_str(item);
-            acc.push_str(", ");
-            acc
-        })
-        .trim_end_matches(", ")
-        .to_owned()
+    fields.iter().map(|ref field| &field.name).format("`, `").to_string()
 }
 
 pub(crate) fn render_object_field(