[Resolver] Add rudimentary lockfile handling, equivalent to the old behavior

lib/cocoapods/installer/analyzer.rb

@@ -241,7 +241,7 @@ module Pod
           locking_pods = result.podfile_state.unchanged
           if update_mode == :selected
             # If selected Pods should been updated, filter them out of the list
-            locking_pods = locking_pods.select { |pod| !update[:pods].include?(pod) }
+            locking_pods = locking_pods.reject { |pod| update[:pods].include?(pod) }
           end
           locking_pods.map do |pod|
             lockfile.dependencies_to_lock_pod_named(pod)

lib/cocoapods/resolver.rb

@@ -87,7 +87,9 @@ module Pod
       @activated = ::Resolver::Resolver.new(self,self).
         resolve(
           @podfile.target_definition_list.map(&:dependencies).flatten,
-          ::Resolver::DependencyGraph.new
+          locked_dependencies.reduce(::Resolver::DependencyGraph.new) do |graph, locked|
+            graph.tap { |g| g.add_root_vertex(locked.name, locked) }
+          end
         )
       specs_by_target
     rescue ::Resolver::ResolverError => e

master @ b6e1c242

-Subproject commit b0f4e85738f1f911e32e2914b39e9acdce7c7ed9
+Subproject commit b6e1c2429964b4e47b344958572930e15ffbbcea

spec/unit/resolver_spec.rb

@@ -228,7 +228,7 @@ SPEC CHECKSUMS:
 COCOAPODS: 0.33.1
         EOS
         lockfile = Lockfile.new(YAMLHelper.load_string(lockfile_yaml))
-        resolver = Resolver.new(config.sandbox, podfile, lockfile.dependencies, SourcesManager.all)
+        resolver = Resolver.new(config.sandbox, podfile, lockfile.dependencies, SourcesManager.master)
         resolver.resolve.values.first.
           find { |s| s.name == 'Mixpanel' }.
           version.to_s.should == '2.5.1'