diff --git a/vendor/go.etcd.io/etcd/pkg/flags/flag.go b/vendor/go.etcd.io/etcd/pkg/flags/flag.go
new file mode 100644
index 0000000..215902c
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/pkg/flags/flag.go
@@ -0,0 +1,121 @@
+// Copyright 2015 The etcd Authors
+//
+// 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 flags implements command-line flag parsing.
+package flags
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/coreos/pkg/capnslog"
+	"github.com/spf13/pflag"
+)
+
+var plog = capnslog.NewPackageLogger("go.etcd.io/etcd", "pkg/flags")
+
+// SetFlagsFromEnv parses all registered flags in the given flagset,
+// and if they are not already set it attempts to set their values from
+// environment variables. Environment variables take the name of the flag but
+// are UPPERCASE, have the given prefix  and any dashes are replaced by
+// underscores - for example: some-flag => ETCD_SOME_FLAG
+func SetFlagsFromEnv(prefix string, fs *flag.FlagSet) error {
+	var err error
+	alreadySet := make(map[string]bool)
+	fs.Visit(func(f *flag.Flag) {
+		alreadySet[FlagToEnv(prefix, f.Name)] = true
+	})
+	usedEnvKey := make(map[string]bool)
+	fs.VisitAll(func(f *flag.Flag) {
+		if serr := setFlagFromEnv(fs, prefix, f.Name, usedEnvKey, alreadySet, true); serr != nil {
+			err = serr
+		}
+	})
+	verifyEnv(prefix, usedEnvKey, alreadySet)
+	return err
+}
+
+// SetPflagsFromEnv is similar to SetFlagsFromEnv. However, the accepted flagset type is pflag.FlagSet
+// and it does not do any logging.
+func SetPflagsFromEnv(prefix string, fs *pflag.FlagSet) error {
+	var err error
+	alreadySet := make(map[string]bool)
+	usedEnvKey := make(map[string]bool)
+	fs.VisitAll(func(f *pflag.Flag) {
+		if f.Changed {
+			alreadySet[FlagToEnv(prefix, f.Name)] = true
+		}
+		if serr := setFlagFromEnv(fs, prefix, f.Name, usedEnvKey, alreadySet, false); serr != nil {
+			err = serr
+		}
+	})
+	verifyEnv(prefix, usedEnvKey, alreadySet)
+	return err
+}
+
+// FlagToEnv converts flag string to upper-case environment variable key string.
+func FlagToEnv(prefix, name string) string {
+	return prefix + "_" + strings.ToUpper(strings.Replace(name, "-", "_", -1))
+}
+
+func verifyEnv(prefix string, usedEnvKey, alreadySet map[string]bool) {
+	for _, env := range os.Environ() {
+		kv := strings.SplitN(env, "=", 2)
+		if len(kv) != 2 {
+			plog.Warningf("found invalid env %s", env)
+		}
+		if usedEnvKey[kv[0]] {
+			continue
+		}
+		if alreadySet[kv[0]] {
+			plog.Fatalf("conflicting environment variable %q is shadowed by corresponding command-line flag (either unset environment variable or disable flag)", kv[0])
+		}
+		if strings.HasPrefix(env, prefix+"_") {
+			plog.Warningf("unrecognized environment variable %s", env)
+		}
+	}
+}
+
+type flagSetter interface {
+	Set(fk string, fv string) error
+}
+
+func setFlagFromEnv(fs flagSetter, prefix, fname string, usedEnvKey, alreadySet map[string]bool, log bool) error {
+	key := FlagToEnv(prefix, fname)
+	if !alreadySet[key] {
+		val := os.Getenv(key)
+		if val != "" {
+			usedEnvKey[key] = true
+			if serr := fs.Set(fname, val); serr != nil {
+				return fmt.Errorf("invalid value %q for %s: %v", val, key, serr)
+			}
+			if log {
+				plog.Infof("recognized and used environment variable %s=%s", key, val)
+			}
+		}
+	}
+	return nil
+}
+
+func IsSet(fs *flag.FlagSet, name string) bool {
+	set := false
+	fs.Visit(func(f *flag.Flag) {
+		if f.Name == name {
+			set = true
+		}
+	})
+	return set
+}