Refactor Source and SourceRegistry.

lib/src/command/cache_repair.dart

Index: lib/src/command/cache_repair.dart
diff --git a/lib/src/command/cache_repair.dart b/lib/src/command/cache_repair.dart
index 5d7ab94a8e737764edf8a22dbbeeb63da4c38a84..cf7e6512b568fb6311f82fac3dea91c870d2ba7f 100644
--- a/lib/src/command/cache_repair.dart
+++ b/lib/src/command/cache_repair.dart
@@ -24,7 +24,8 @@ class CacheRepairCommand extends PubCommand {
     var failures = [];
 
     // Repair every cached source.
-    for (var source in cache.sources) {
+    for (var source in cache.sources.all
+       .map((source) => cache.source(source.name))) {
       if (source is! CachedSource) continue;
 
       var results = await source.repairCachedPackages();