feat(api): add build configurations per FileTree entry (#3523)

diff --git a/kythe/proto/filetree.proto b/kythe/proto/filetree.proto
index 02bb08b..0c8cfde 100644
--- a/kythe/proto/filetree.proto
+++ b/kythe/proto/filetree.proto
@@ -64,7 +64,9 @@
     // The basename of the entry within the directory.
     string name = 2;
 
-    // TODO(schroederc): repeated string build_configuration = 3;
+    // Set of known build configurations of this FILE or all files recursively
+    // contained in/below this DIRECTORY.
+    repeated string build_configuration = 3;
   }
   enum Kind {
     UNKNOWN = 0;
diff --git a/kythe/proto/filetree_go_proto/filetree.pb.go b/kythe/proto/filetree_go_proto/filetree.pb.go
index 4a53092..862509d 100644
--- a/kythe/proto/filetree_go_proto/filetree.pb.go
+++ b/kythe/proto/filetree_go_proto/filetree.pb.go
@@ -41,7 +41,7 @@
 	return proto.EnumName(DirectoryReply_Kind_name, int32(x))
 }
 func (DirectoryReply_Kind) EnumDescriptor() ([]byte, []int) {
-	return fileDescriptor_filetree_2585d68aef5af310, []int{3, 0}
+	return fileDescriptor_filetree_e57c3a9b3f8d6f2b, []int{3, 0}
 }
 
 type CorpusRootsRequest struct {
@@ -54,7 +54,7 @@
 func (m *CorpusRootsRequest) String() string { return proto.CompactTextString(m) }
 func (*CorpusRootsRequest) ProtoMessage()    {}
 func (*CorpusRootsRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_filetree_2585d68aef5af310, []int{0}
+	return fileDescriptor_filetree_e57c3a9b3f8d6f2b, []int{0}
 }
 func (m *CorpusRootsRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CorpusRootsRequest.Unmarshal(m, b)
@@ -85,7 +85,7 @@
 func (m *CorpusRootsReply) String() string { return proto.CompactTextString(m) }
 func (*CorpusRootsReply) ProtoMessage()    {}
 func (*CorpusRootsReply) Descriptor() ([]byte, []int) {
-	return fileDescriptor_filetree_2585d68aef5af310, []int{1}
+	return fileDescriptor_filetree_e57c3a9b3f8d6f2b, []int{1}
 }
 func (m *CorpusRootsReply) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CorpusRootsReply.Unmarshal(m, b)
@@ -124,7 +124,7 @@
 func (m *CorpusRootsReply_Corpus) String() string { return proto.CompactTextString(m) }
 func (*CorpusRootsReply_Corpus) ProtoMessage()    {}
 func (*CorpusRootsReply_Corpus) Descriptor() ([]byte, []int) {
-	return fileDescriptor_filetree_2585d68aef5af310, []int{1, 0}
+	return fileDescriptor_filetree_e57c3a9b3f8d6f2b, []int{1, 0}
 }
 func (m *CorpusRootsReply_Corpus) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CorpusRootsReply_Corpus.Unmarshal(m, b)
@@ -171,7 +171,7 @@
 func (m *DirectoryRequest) String() string { return proto.CompactTextString(m) }
 func (*DirectoryRequest) ProtoMessage()    {}
 func (*DirectoryRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_filetree_2585d68aef5af310, []int{2}
+	return fileDescriptor_filetree_e57c3a9b3f8d6f2b, []int{2}
 }
 func (m *DirectoryRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_DirectoryRequest.Unmarshal(m, b)
@@ -228,7 +228,7 @@
 func (m *DirectoryReply) String() string { return proto.CompactTextString(m) }
 func (*DirectoryReply) ProtoMessage()    {}
 func (*DirectoryReply) Descriptor() ([]byte, []int) {
-	return fileDescriptor_filetree_2585d68aef5af310, []int{3}
+	return fileDescriptor_filetree_e57c3a9b3f8d6f2b, []int{3}
 }
 func (m *DirectoryReply) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_DirectoryReply.Unmarshal(m, b)
@@ -295,6 +295,7 @@
 type DirectoryReply_Entry struct {
 	Kind                 DirectoryReply_Kind `protobuf:"varint,1,opt,name=kind,proto3,enum=kythe.proto.DirectoryReply_Kind" json:"kind,omitempty"`
 	Name                 string              `protobuf:"bytes,2,opt,name=name,proto3" json:"name,omitempty"`
+	BuildConfiguration   []string            `protobuf:"bytes,3,rep,name=build_configuration,json=buildConfiguration,proto3" json:"build_configuration,omitempty"`
 	XXX_NoUnkeyedLiteral struct{}            `json:"-"`
 	XXX_unrecognized     []byte              `json:"-"`
 	XXX_sizecache        int32               `json:"-"`
@@ -304,7 +305,7 @@
 func (m *DirectoryReply_Entry) String() string { return proto.CompactTextString(m) }
 func (*DirectoryReply_Entry) ProtoMessage()    {}
 func (*DirectoryReply_Entry) Descriptor() ([]byte, []int) {
-	return fileDescriptor_filetree_2585d68aef5af310, []int{3, 0}
+	return fileDescriptor_filetree_e57c3a9b3f8d6f2b, []int{3, 0}
 }
 func (m *DirectoryReply_Entry) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_DirectoryReply_Entry.Unmarshal(m, b)
@@ -338,6 +339,13 @@
 	return ""
 }
 
+func (m *DirectoryReply_Entry) GetBuildConfiguration() []string {
+	if m != nil {
+		return m.BuildConfiguration
+	}
+	return nil
+}
+
 func init() {
 	proto.RegisterType((*CorpusRootsRequest)(nil), "kythe.proto.CorpusRootsRequest")
 	proto.RegisterType((*CorpusRootsReply)(nil), "kythe.proto.CorpusRootsReply")
@@ -349,36 +357,37 @@
 }
 
 func init() {
-	proto.RegisterFile("kythe/proto/filetree.proto", fileDescriptor_filetree_2585d68aef5af310)
+	proto.RegisterFile("kythe/proto/filetree.proto", fileDescriptor_filetree_e57c3a9b3f8d6f2b)
 }
 
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