progress: auto-select progress type on "" based on if there is a pty

This commit adds support to auto-select the terminal based on if
it is a pty or not.

bib/internal/progress/progress.go

@@ -40,7 +40,15 @@ type ProgressBar interface {
 // New creates a new progressbar based on the requested type
 func New(typ string) (ProgressBar, error) {
 	switch typ {
-	case "", "plain":
+	case "":
+		// auto-select
+		if f, ok := osStderr.(*os.File); ok {
+			if isatty.IsTerminal(f.Fd()) {
+				return NewTermProgressBar()
+			}
+		}
+		return NewPlainProgressBar()
+	case "plain":
 		return NewPlainProgressBar()
 	case "term":
 		return NewTermProgressBar()

bib/internal/progress/progress_test.go

@@ -7,7 +7,6 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 
 	"github.com/osbuild/bootc-image-builder/bib/internal/progress"
 )
@@ -24,6 +23,7 @@ func TestProgressNew(t *testing.T) {
 		{"term", &progress.TermProgressBar{}, ""},
 		{"debug", &progress.DebugProgressBar{}, ""},
 		{"plain", &progress.PlainProgressBar{}, ""},
+		// unknown progress type
 		{"bad", nil, `unknown progress type: "bad"`},
 	} {
 		pb, err := progress.New(tc.typ)
@@ -36,6 +36,19 @@ func TestProgressNew(t *testing.T) {
 	}
 }
 
+func TestProgressNewAutoSelect(t *testing.T) {
+	var buf bytes.Buffer
+	restore := progress.MockOsStderr(&buf)
+	defer restore()
+
+	// XXX: test auto-select terminal case by mocking osStderr via
+	// terminal
+	pb, err := progress.New("")
+	assert.NoError(t, err)
+	expected := &progress.PlainProgressBar{}
+	assert.Equal(t, reflect.TypeOf(pb), reflect.TypeOf(expected))
+}
+
 func TestPlainProgress(t *testing.T) {
 	var buf bytes.Buffer
 	restore := progress.MockOsStderr(&buf)