Use github.com/spf13/cobra module to generate command line interface

go.mod

@@ -7,7 +7,8 @@ require (
 	github.com/arduino/go-paths-helper v1.6.1
 	github.com/arduino/golang-concurrent-workers v0.0.0-20170202182617-6710cdc954bc
 	github.com/go-git/go-git/v5 v5.4.2
-	github.com/google/go-cmp v0.5.2 // indirect
+	github.com/spf13/cobra v1.2.1
+	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.7.0
 	github.com/vaughan0/go-ini v0.0.0-20130923145212-a98ad7ee00ec
 	go.bug.st/relaxed-semver v0.0.0-20190922224835-391e10178d18

internal/cli/root.go

@@ -0,0 +1,82 @@
+// This file is part of libraries-repository-engine.
+//
+// Copyright 2021 ARDUINO SA (http://www.arduino.cc/)
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
+// Package cli defines the command line interface.
+package cli
+
+import (
+	"os"
+
+	"github.com/arduino/libraries-repository-engine/internal/feedback"
+	"github.com/spf13/cobra"
+)
+
+// rootCmd defines the base CLI command.
+var rootCmd = &cobra.Command{
+	Use:  "libraries-repository-engine",
+	Long: "The tool for managing the Arduino Library Manager content.",
+	CompletionOptions: cobra.CompletionOptions{
+		DisableDefaultCmd: true,
+	},
+	Aliases: []string{"sync"},
+}
+
+func init() {
+	rootCmd.PersistentFlags().String("config-file", "config.json", "Configuration file path")
+}
+
+// Execute adds all child commands to the root command and sets flags appropriately.
+func Execute() error {
+	// Support the old `libraries-repository-engine [CONFIG_FILE [REGISTRY_FILE]]` interface.
+	func() {
+		if len(os.Args) > 1 {
+			if os.Args[1][0] == '-' {
+				// The argument is a flag, so assume the new interface.
+				return
+			}
+
+			for _, command := range rootCmd.Commands() {
+				for _, alias := range append(command.Aliases, command.Name(), "help") { // Hacky to check "help" redundantly, but whatever.
+					if os.Args[1] == alias {
+						// The argument is a registered subcommand, so assume the new interface.
+						return
+					}
+				}
+			}
+
+			// The argument is not a registered subcommand, so assume it is the CONFIG_FILE positional argument of the old interface.
+			rootCmd.PersistentFlags().Set("config-file", os.Args[1]) // Transfer the argument to the new interface's flag.
+			os.Args = append([]string{os.Args[0]}, os.Args[2:]...)   // Remove the argument.
+		}
+
+		feedback.Warning(
+			`Using deprecated command line syntax. New syntax:
+libraries-repository-engine sync [--config-file=CONFIG_FILE] [REGISTRY_FILE]
+`,
+		)
+		// Set the subcommand to the root's alias.
+		os.Args = append([]string{os.Args[0], rootCmd.Aliases[0]}, os.Args[1:]...)
+	}()
+
+	return rootCmd.Execute()
+}

internal/cli/sync.go

@@ -0,0 +1,49 @@
+// This file is part of libraries-repository-engine.
+//
+// Copyright 2021 ARDUINO SA (http://www.arduino.cc/)
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
+package cli
+
+import (
+	"github.com/arduino/libraries-repository-engine/internal/command/sync"
+	"github.com/spf13/cobra"
+)
+
+// syncCmd defines the `sync` CLI subcommand.
+var syncCmd = &cobra.Command{
+	Short:                 "Update Library Manager content",
+	Long:                  "Update the Library Manager content",
+	DisableFlagsInUseLine: true,
+	Use: `sync [FLAG]... [REGISTRY_FILE_PATH]
+
+For each of the library registrations in the file at REGISTRY_FILE_PATH:
+
+- check their repository for tags not already in the database
+- check whether the new tag meets the requirements for addition to the index
+- add library release to the database and store archive for the compliant tag
+- generate the Library Manager index file`,
+	Run: sync.Run,
+}
+
+func init() {
+	rootCmd.AddCommand(syncCmd)
+}