Improve experience for multiple builtin templates (#1052)

## Changes
This enhances the template selection experience a bit as we add more and
more built-in templates (like
https://github.com/databricks/cli/pull/1051 and
https://github.com/databricks/cli/pull/1059):

### New experience:
<img width="661" alt="image"
src="https://github.com/databricks/cli/assets/58432911/afe3b84d-8a77-47f3-b9c2-f827f7893cd7">

### Current experience:
<img width="265" alt="image"
src="https://github.com/databricks/cli/assets/58432911/36f8d568-819f-4920-83b1-fb76109ea3d1">

---------

Co-authored-by: shreyas-goenka <88374338+shreyas-goenka@users.noreply.github.com>

cmd/bundle/init.go

@@ -27,35 +27,58 @@ type nativeTemplate struct {
 	aliases     []string
 }
 
+const customTemplate = "custom..."
+
 var nativeTemplates = []nativeTemplate{
 	{
 		name:        "default-python",
-		description: "The default Python template",
+		description: "The default Python template for Notebooks / Delta Live Tables / Workflows",
 	},
 	{
 		name:        "mlops-stacks",
 		gitUrl:      "https://github.com/databricks/mlops-stacks",
-		description: "The Databricks MLOps Stacks template (https://github.com/databricks/mlops-stacks)",
+		description: "The Databricks MLOps Stacks template (github.com/databricks/mlops-stacks)",
 		aliases:     []string{"mlops-stack"},
 	},
+	{
+		name:        customTemplate,
+		description: "Bring your own template",
+	},
 }
 
-func nativeTemplateDescriptions() string {
+// Return template descriptions for command-line help
+func nativeTemplateHelpDescriptions() string {
 	var lines []string
 	for _, template := range nativeTemplates {
-		lines = append(lines, fmt.Sprintf("- %s: %s", template.name, template.description))
+		if template.name != customTemplate {
+			lines = append(lines, fmt.Sprintf("- %s: %s", template.name, template.description))
+		}
 	}
 	return strings.Join(lines, "\n")
 }
 
-func nativeTemplateOptions() []string {
-	names := make([]string, 0, len(nativeTemplates))
+// Return template options for an interactive prompt
+func nativeTemplateOptions() []cmdio.Tuple {
+	names := make([]cmdio.Tuple, 0, len(nativeTemplates))
 	for _, template := range nativeTemplates {
-		names = append(names, template.name)
+		tuple := cmdio.Tuple{
+			Name: template.name,
+			Id:   template.description,
+		}
+		names = append(names, tuple)
 	}
 	return names
 }
 
+func getNativeTemplateByDescription(description string) string {
+	for _, template := range nativeTemplates {
+		if template.description == description {
+			return template.name
+		}
+	}
+	return ""
+}
+
 func getUrlForNativeTemplate(name string) string {
 	for _, template := range nativeTemplates {
 		if template.name == name {
@@ -99,7 +122,7 @@ TEMPLATE_PATH optionally specifies which template to use. It can be one of the f
 - a local file system path with a template directory
 - a Git repository URL, e.g. https://github.com/my/repository
 
-See https://docs.databricks.com/en/dev-tools/bundles/templates.html for more information on templates.`, nativeTemplateDescriptions()),
+See https://docs.databricks.com/en/dev-tools/bundles/templates.html for more information on templates.`, nativeTemplateHelpDescriptions()),
 	}
 
 	var configFile string
@@ -134,10 +157,17 @@ See https://docs.databricks.com/en/dev-tools/bundles/templates.html for more inf
 			if !cmdio.IsPromptSupported(ctx) {
 				return errors.New("please specify a template")
 			}
-			templatePath, err = cmdio.AskSelect(ctx, "Template to use", nativeTemplateOptions())
+			description, err := cmdio.SelectOrdered(ctx, nativeTemplateOptions(), "Template to use")
 			if err != nil {
 				return err
 			}
+			templatePath = getNativeTemplateByDescription(description)
+		}
+
+		if templatePath == customTemplate {
+			cmdio.LogString(ctx, "Please specify a path or Git repository to use a custom template.")
+			cmdio.LogString(ctx, "See https://docs.databricks.com/en/dev-tools/bundles/templates.html to learn more about custom templates.")
+			return nil
 		}
 
 		// Expand templatePath to a git URL if it's an alias for a known native template

cmd/bundle/init_test.go

@@ -3,6 +3,7 @@ package bundle
 import (
 	"testing"
 
+	"github.com/databricks/cli/libs/cmdio"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -27,11 +28,18 @@ func TestBundleInitRepoName(t *testing.T) {
 }
 
 func TestNativeTemplateOptions(t *testing.T) {
-	assert.Equal(t, []string{"default-python", "mlops-stacks"}, nativeTemplateOptions())
+	expected := []cmdio.Tuple{
+		{Name: "default-python", Id: "The default Python template for Notebooks / Delta Live Tables / Workflows"},
+		{Name: "mlops-stacks", Id: "The Databricks MLOps Stacks template (github.com/databricks/mlops-stacks)"},
+		{Name: "custom...", Id: "Bring your own template"},
+	}
+	assert.Equal(t, expected, nativeTemplateOptions())
 }
 
-func TestNativeTemplateDescriptions(t *testing.T) {
-	assert.Equal(t, "- default-python: The default Python template\n- mlops-stacks: The Databricks MLOps Stacks template (https://github.com/databricks/mlops-stacks)", nativeTemplateDescriptions())
+func TestNativeTemplateHelpDescriptions(t *testing.T) {
+	expected := `- default-python: The default Python template for Notebooks / Delta Live Tables / Workflows
+- mlops-stacks: The Databricks MLOps Stacks template (github.com/databricks/mlops-stacks)`
+	assert.Equal(t, expected, nativeTemplateHelpDescriptions())
 }
 
 func TestGetUrlForNativeTemplate(t *testing.T) {

libs/cmdio/io.go

@@ -155,19 +155,13 @@ func RenderReader(ctx context.Context, r io.Reader) error {
 	}
 }
 
-type tuple struct{ Name, Id string }
+type Tuple struct{ Name, Id string }
 
-func (c *cmdIO) Select(names map[string]string, label string) (id string, err error) {
+func (c *cmdIO) Select(items []Tuple, label string) (id string, err error) {
 	if !c.interactive {
 		return "", fmt.Errorf("expected to have %s", label)
 	}
-	var items []tuple
-	for k, v := range names {
-		items = append(items, tuple{k, v})
-	}
-	slices.SortFunc(items, func(a, b tuple) int {
-		return strings.Compare(a.Name, b.Name)
-	})
+
 	idx, _, err := (&promptui.Select{
 		Label:             label,
 		Items:             items,
@@ -190,13 +184,25 @@ func (c *cmdIO) Select(names map[string]string, label string) (id string, err er
 	return
 }
 
+// Show a selection prompt where the user can pick one of the name/id items.
+// The items are sorted alphabetically by name.
 func Select[V any](ctx context.Context, names map[string]V, label string) (id string, err error) {
 	c := fromContext(ctx)
-	stringNames := map[string]string{}
+	var items []Tuple
 	for k, v := range names {
-		stringNames[k] = fmt.Sprint(v)
+		items = append(items, Tuple{k, fmt.Sprint(v)})
 	}
-	return c.Select(stringNames, label)
+	slices.SortFunc(items, func(a, b Tuple) int {
+		return strings.Compare(a.Name, b.Name)
+	})
+	return c.Select(items, label)
+}
+
+// Show a selection prompt where the user can pick one of the name/id items.
+// The items appear in the order specified in the "items" argument.
+func SelectOrdered(ctx context.Context, items []Tuple, label string) (id string, err error) {
+	c := fromContext(ctx)
+	return c.Select(items, label)
 }
 
 func (c *cmdIO) Secret(label string) (value string, err error) {