switch to go-kit/log (#1575)

Signed-off-by: yeya24 <yb532204897@gmail.com>

vendor/github.com/prometheus/common/promlog/flag/flag.go

@@ -0,0 +1,45 @@
+// Copyright 2017 The Prometheus 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 flag
+
+import (
+	"github.com/prometheus/common/promlog"
+	kingpin "gopkg.in/alecthomas/kingpin.v2"
+)
+
+// LevelFlagName is the canonical flag name to configure the allowed log level
+// within Prometheus projects.
+const LevelFlagName = "log.level"
+
+// LevelFlagHelp is the help description for the log.level flag.
+const LevelFlagHelp = "Only log messages with the given severity or above. One of: [debug, info, warn, error]"
+
+// FormatFlagName is the canonical flag name to configure the log format
+// within Prometheus projects.
+const FormatFlagName = "log.format"
+
+// FormatFlagHelp is the help description for the log.format flag.
+const FormatFlagHelp = "Output format of log messages. One of: [logfmt, json]"
+
+// AddFlags adds the flags used by this package to the Kingpin application.
+// To use the default Kingpin application, call AddFlags(kingpin.CommandLine)
+func AddFlags(a *kingpin.Application, config *promlog.Config) {
+	config.Level = &promlog.AllowedLevel{}
+	a.Flag(LevelFlagName, LevelFlagHelp).
+		Default("info").SetValue(config.Level)
+
+	config.Format = &promlog.AllowedFormat{}
+	a.Flag(FormatFlagName, FormatFlagHelp).
+		Default("logfmt").SetValue(config.Format)
+}