Add version flag to print version and exit (#394)

## Changes

With this PR, all of the command below print version and exit:
```
$ databricks -v
Databricks CLI v0.100.1-dev+4d3fa76
$ databricks --version
Databricks CLI v0.100.1-dev+4d3fa76
$ databricks version  
Databricks CLI v0.100.1-dev+4d3fa76
```

## Tests

Added integration test for each flag or command.

cmd/root/root.go

@@ -17,6 +17,7 @@ import (
 var RootCmd = &cobra.Command{
 	Use:     "databricks",
 	Short:   "Databricks CLI",
+	Version: build.GetInfo().Version,
 
 	// Cobra prints the usage string to stderr if a command returns an error.
 	// This usage string should only be displayed if an invalid combination of flags
@@ -105,9 +106,5 @@ func Execute() {
 
 func init() {
 	RootCmd.SetFlagErrorFunc(flagErrorFunc)
-
-	// The VS Code extension passes `-v` in debug mode and must be changed
-	// to use the new flags in `./logger.go` prior to removing this flag.
-	RootCmd.PersistentFlags().BoolP("verbose", "v", false, "")
-	RootCmd.PersistentFlags().MarkHidden("verbose")
+	RootCmd.SetVersionTemplate("Databricks CLI v{{.Version}}\n")
 }

cmd/version/version.go

@@ -23,8 +23,8 @@ var versionCmd = &cobra.Command{
 			return enc.Encode(info)
 		}
 
-		fmt.Fprintln(cmd.OutOrStdout(), info.Version)
-		return nil
+		_, err := fmt.Fprintf(cmd.OutOrStdout(), "Databricks CLI v%s\n", info.Version)
+		return err
 	},
 }
 

internal/helpers.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/databricks/cli/cmd/root"
+	_ "github.com/databricks/cli/cmd/version"
 	"github.com/stretchr/testify/require"
 )
 

internal/version_test.go

@@ -0,0 +1,29 @@
+package internal
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/databricks/cli/internal/build"
+	"github.com/stretchr/testify/assert"
+)
+
+var expectedVersion = fmt.Sprintf("Databricks CLI v%s\n", build.GetInfo().Version)
+
+func TestVersionFlagShort(t *testing.T) {
+	stdout, stderr := RequireSuccessfulRun(t, "-v")
+	assert.Equal(t, expectedVersion, stdout.String())
+	assert.Equal(t, "", stderr.String())
+}
+
+func TestVersionFlagLong(t *testing.T) {
+	stdout, stderr := RequireSuccessfulRun(t, "--version")
+	assert.Equal(t, expectedVersion, stdout.String())
+	assert.Equal(t, "", stderr.String())
+}
+
+func TestVersionCommand(t *testing.T) {
+	stdout, stderr := RequireSuccessfulRun(t, "version")
+	assert.Equal(t, expectedVersion, stdout.String())
+	assert.Equal(t, "", stderr.String())
+}