Add BoolFlag for rawdatastore.

service/rawdatastore/types.go

Index: service/rawdatastore/types.go
diff --git a/service/rawdatastore/types.go b/service/rawdatastore/types.go
index 9b426ad3ff4e35db1ba2213610aa9b6c37aae61d..e283fa50b36a2f1e5444e75148bb6578f527209d 100644
--- a/service/rawdatastore/types.go
+++ b/service/rawdatastore/types.go
@@ -4,6 +4,10 @@
 
 package rawdatastore
 
+import (
+	"fmt"
+)
+
 // ByteString is a short byte slice (up to 1500 bytes) that can be indexed.
 type ByteString []byte
 
@@ -37,3 +41,27 @@ type TransactionOptions struct {
 	// due to a conflicting transaction. If omitted, it defaults to 3.
 	Attempts int
 }
+
+// BoolFlag is a tri-state boolean (Auto/True/False), which allows structs
+// to control boolean flags for metadata in a non-ambiguous way.
+type BoolFlag byte
+
+// These are the allowed values for BoolFlag. Any other values are invalid.
+const (
+	Auto BoolFlag = iota
+	True
+	False
+)
+
+func (b BoolFlag) String() string {
+	switch b {
+	case Auto:
+		return "Auto"
+	case True:
+		return "True"

[dnj (Google), 2015/07/24 16:11:37]

not: Perhaps lowercase "true"/"false", as that's what it is being parsed from.

+	case False:
+		return "False"
+	default:
+		return fmt.Sprintf("UNKNOWN_BoolFlag(%d)", b)
+	}
+}