Support filegroups

filegroup is a module that contains a list of files, and can be used
to export files across package boundaries.  filegroups (and genrules)
can be referenced from srcs properties of other modules using the
syntax ":module".

Test: m -j
Change-Id: I3d6fc4819c0b4225b474e0ad42f0d947f55a5961
diff --git a/genrule/filegroup.go b/genrule/filegroup.go
new file mode 100644
index 0000000..9b53c9f
--- /dev/null
+++ b/genrule/filegroup.go
@@ -0,0 +1,61 @@
+// Copyright 2016 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package genrule
+
+import (
+	"github.com/google/blueprint"
+
+	"android/soong/android"
+)
+
+func init() {
+	android.RegisterModuleType("filegroup", fileGroupFactory)
+}
+
+type fileGroupProperties struct {
+	// srcs lists files that will be included in this filegroup
+	Srcs []string
+
+	Exclude_srcs []string
+}
+
+type fileGroup struct {
+	android.ModuleBase
+	properties fileGroupProperties
+	srcs       android.Paths
+}
+
+var _ android.SourceFileProducer = (*fileGroup)(nil)
+
+// filegroup modules contain a list of files, and can be used to export files across package
+// boundaries.  filegroups (and genrules) can be referenced from srcs properties of other modules
+// using the syntax ":module".
+func fileGroupFactory() (blueprint.Module, []interface{}) {
+	module := &fileGroup{}
+
+	return android.InitAndroidModule(module, &module.properties)
+}
+
+func (fg *fileGroup) DepsMutator(ctx android.BottomUpMutatorContext) {
+	android.ExtractSourcesDeps(ctx, fg.properties.Srcs)
+}
+
+func (fg *fileGroup) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	fg.srcs = ctx.ExpandSources(fg.properties.Srcs, fg.properties.Exclude_srcs)
+}
+
+func (fg *fileGroup) Srcs() android.Paths {
+	return fg.srcs
+}