Preserve previous trailing-comma behavior

Because most likely there are quickly enough tables in there that it is formatted with one table per line, for which the best display is then to have the trailing comma, for the same rationale as rustfmt describes.

(Also that should fix tests)

diesel_cli/src/print_schema.rs

@@ -6,8 +6,7 @@ use serde::{Deserialize, Serialize};
 use std::collections::{BTreeSet, HashSet};
 use std::fmt::{self, Display, Formatter, Write};
 use std::io::Write as IoWrite;
-use std::process;
-use std::str;
+use std::{process, str};
 
 const SCHEMA_HEADER: &str = "// @generated automatically by Diesel CLI.\n";
 
@@ -598,11 +597,8 @@ impl Display for TableDefinitions<'_> {
             {
                 let mut out = PadAdapter::new(f);
                 writeln!(out)?;
-                for (table_index, table) in table_group.into_iter().enumerate() {
-                    if table_index != 0 {
-                        write!(out, ", ")?;
-                    }
-                    write!(out, "{}", table.rust_name)?;
+                for table in table_group {
+                    write!(out, "{},", table.rust_name)?;
                 }
             }
             writeln!(f, ");")?;

diesel_cli/tests/print_schema/print_schema_fk_related_tables/postgres/expected.snap

@@ -55,5 +55,5 @@ diesel::joinable!(comments -> posts (post_id));
 diesel::joinable!(posts -> users (user_id));
 diesel::joinable!(transactions -> sessions (session_id));
 
-diesel::allow_tables_to_appear_in_same_query!(comments, posts, users);
-diesel::allow_tables_to_appear_in_same_query!(sessions, transactions);
+diesel::allow_tables_to_appear_in_same_query!(comments, posts, users,);
+diesel::allow_tables_to_appear_in_same_query!(sessions, transactions,);