refactor(github): fetch raw markdown

lib/models/auth.dart

@@ -287,14 +287,9 @@ class AuthModel with ChangeNotifier {
     return data['data'];
   }
 
-  Future<dynamic> getWithCredentials(String url, {String contentType}) async {
-    var headers = _headers;
-    if (contentType != null) {
-      // https://developer.github.com/v3/repos/contents/#custom-media-types
-      headers[HttpHeaders.contentTypeHeader] = contentType;
-    }
+  Future<dynamic> getWithCredentials(String url) async {
     final res = await http
-        .get(_apiPrefix + url, headers: headers)
+        .get(_apiPrefix + url, headers: _headers)
         .timeout(_timeoutDuration);
     final data = json.decode(res.body);
     if (res.statusCode >= 400) {
@@ -303,6 +298,15 @@ class AuthModel with ChangeNotifier {
     return data;
   }
 
+  Future<String> getRaw(String url) async {
+    final res = await http.get(_apiPrefix + url, headers: {
+      ..._headers,
+      // https://developer.github.com/v3/repos/contents/#custom-media-types
+      HttpHeaders.acceptHeader: 'application/vnd.github.v3.raw'
+    }).timeout(_timeoutDuration);
+    return res.body;
+  }
+
   Future<void> patchWithCredentials(String url) async {
     await http
         .patch(_apiPrefix + url, headers: _headers)

lib/screens/repository.dart

@@ -1,4 +1,3 @@
-import 'dart:convert';
 import 'package:filesize/filesize.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/cupertino.dart';
@@ -46,12 +45,6 @@ class RepositoryScreen extends StatelessWidget {
     return res.data.repository;
   }
 
-  Future<String> _fetchReadme(BuildContext context) async {
-    final data = await Provider.of<AuthModel>(context)
-        .getWithCredentials('/repos/$owner/$name/readme');
-    return (data['content'] as String)?.dropLineBreak?.base64ToUtf8;
-  }
-
   Widget _buildLanguages(BuildContext context, GhRepoRepository repo) {
     final theme = Provider.of<ThemeModel>(context);
     return Container(
@@ -106,7 +99,7 @@ class RepositoryScreen extends StatelessWidget {
       fetchData: () async {
         final rs = await Future.wait([
           _query(context),
-          _fetchReadme(context),
+          Provider.of<AuthModel>(context).getRaw('/repos/$owner/$name/readme'),
         ]);
         return Tuple2(rs[0] as GhRepoRepository, rs[1] as String);
       },