Add stub nvidia-ctk CLI

This change adds an nvidia-ctk CLI that is used as the basis for
utilities related to the NVIDIA Container Toolkit.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

.gitignore

@@ -5,4 +5,5 @@ dist
 /test/output/
 /nvidia-container-runtime
 /nvidia-container-toolkit
+/nvidia-ctk
 /shared-*

cmd/nvidia-ctk/README.md

@@ -0,0 +1,3 @@
+# NVIDIA Container Toolkit CLI
+
+The NVIDIA Container Toolkit CLI `nvidia-ctk` provides a number of utilities that are useful for working with the NVIDIA Container Toolkit.

cmd/nvidia-ctk/main.go

@@ -0,0 +1,79 @@
+/**
+# Copyright (c) 2021, NVIDIA CORPORATION.  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 main
+
+import (
+	"os"
+
+	log "github.com/sirupsen/logrus"
+	cli "github.com/urfave/cli/v2"
+)
+
+var version string
+
+var logger = log.New()
+
+// config defines the options that can be set for the CLI through config files,
+// environment variables, or command line flags
+type config struct {
+	// Debug indicates whether the CLI is started in "debug" mode
+	Debug bool
+}
+
+func main() {
+	// Create a config struct to hold the parsed environment variables or command line flags
+	config := config{}
+
+	// Create the top-level CLI
+	c := cli.NewApp()
+	c.UseShortOptionHandling = true
+	c.EnableBashCompletion = true
+	c.Usage = "Tools to configure the NVIDIA Container Toolkit"
+	c.Version = version
+
+	// Setup the flags for this command
+	c.Flags = []cli.Flag{
+		&cli.BoolFlag{
+			Name:        "debug",
+			Aliases:     []string{"d"},
+			Usage:       "Enable debug-level logging",
+			Destination: &config.Debug,
+			EnvVars:     []string{"NVIDIA_CTK_DEBUG"},
+		},
+	}
+
+	// Set log-level for all subcommands
+	c.Before = func(c *cli.Context) error {
+		logLevel := log.InfoLevel
+		if config.Debug {
+			logLevel = log.DebugLevel
+		}
+
+		logger.SetLevel(logLevel)
+		return nil
+	}
+
+	// Define the subcommands
+	c.Commands = []*cli.Command{}
+
+	// Run the CLI
+	err := c.Run(os.Args)
+	if err != nil {
+		log.Errorf("%v", err)
+		log.Exit(1)
+	}
+}