feat: make mutate an option within fix mode (fixes #144)

src/app.ts

@@ -37,7 +37,7 @@ export async function main(argv: Array<string>): Promise<number> {
     schemaOptions: {
       coerce: args.coerce,
       defaults: args.defaults,
-      mutate: mode === MODE.fix,
+      mutate: args.mutate,
     },
   });
 

src/config/args.ts

@@ -36,6 +36,7 @@ export interface ParsedArgs extends RuleSelector, RuleSources {
   defaults: boolean;
   dest: string;
   mode: string;
+  mutate: boolean;
   source: string;
 }
 
@@ -68,6 +69,10 @@ export async function parseArgs(argv: Array<string>): Promise<ParseResults> {
           default: true,
           type: 'boolean',
         },
+        mutate: {
+          default: true,
+          type: 'boolean',
+        },
       }),
       command: ['fix'],
       describe: 'validate the source document and insert defaults',