Add version command

This commit adds a command that allows the user to display the version of git-bug-migration.

Author: vincetiu8

Makefile

@@ -4,9 +4,10 @@ GIT_COMMIT:=$(shell git rev-list -1 HEAD)
 GIT_LAST_TAG:=$(shell git describe --abbrev=0 --tags)
 GIT_EXACT_TAG:=$(shell git name-rev --name-only --tags HEAD)
 
-LDFLAGS:=-X 'main.GitCommit=${GIT_COMMIT}' \
-	-X 'main.GitLastTag=${GIT_LAST_TAG}' \
-	-X 'main.GitExactTag=${GIT_EXACT_TAG}'
+COMMANDS_PATH:=github.com/MichaelMure/git-bug-migration/commands
+LDFLAGS:=-X '${COMMANDS_PATH}.GitCommit=${GIT_COMMIT}' \
+	-X '${COMMANDS_PATH}.GitLastTag=${GIT_LAST_TAG}' \
+	-X '${COMMANDS_PATH}.GitExactTag=${GIT_EXACT_TAG}'
 
 build:
 	go build -ldflags "$(LDFLAGS)" .

commands/migrate.go

@@ -9,13 +9,43 @@ import (
 
 	"github.com/spf13/cobra"
 
+	mg1 "github.com/MichaelMure/git-bug-migration/migration1"
 	mg1b "github.com/MichaelMure/git-bug-migration/migration1/bug"
 	mg1r "github.com/MichaelMure/git-bug-migration/migration1/repository"
 )
 
 const rootCommandName = "git-bug-migration"
 
-var repo mg1r.ClockedRepo
+var (
+	repo mg1r.ClockedRepo
+
+	// These variables are initialized externally during the build. See the Makefile.
+	GitCommit   = ""
+	GitLastTag  = ""
+	GitExactTag = ""
+
+	rootCmdShowVersion bool
+)
+
+func runRootCmd(_ *cobra.Command, args []string) error {
+	if rootCmdShowVersion {
+		fmt.Printf(version())
+		return nil
+	}
+
+	return mg1.Migrate01(repo)
+}
+
+func version() string {
+	if GitExactTag == "undefined" {
+		GitExactTag = ""
+	}
+	version := GitLastTag
+	if GitExactTag == "" {
+		version = fmt.Sprintf("%s-dev-%.10s", version, GitCommit)
+	}
+	return version
+}
 
 // RootCmd represents the base command when called without any subcommands
 var RootCmd = &cobra.Command{
@@ -30,7 +60,7 @@ var RootCmd = &cobra.Command{
 	// even if we just display the help. This is to make sure that we check
 	// the repository and give the user early feedback.
 	PreRunE: loadRepo,
-	RunE:    runMigrateCmd,
+	RunE:    runRootCmd,
 
 	SilenceUsage:      true,
 	DisableAutoGenTag: true,
@@ -67,3 +97,10 @@ func Execute() {
 		os.Exit(1)
 	}
 }
+
+func init() {
+	RootCmd.Flags().SortFlags = false
+
+	RootCmd.Flags().BoolVarP(&rootCmdShowVersion, "version", "v", false,
+		"Show the version of the migration tool. This will not run the tool.")
+}