progress: auto-select progress based on the environment

This commit adds automatic progress bar selection based on the
environment. Ideally we would check for a terminal but with
podman we never have one. So we check for TERM and SSH_CONNECTION
and anf if that is used we assume it's an interactive shell and
give the nice "terminalProgressBar". If that is not set we assuem
we run in a script or CI/CD environment and select plainProgressBar.

bib/internal/progress/progress.go

@@ -66,12 +66,29 @@ type ProgressBar interface {
 	Stop()
 }
 
+func isTerminal() bool {
+	// Note that we cannot simply use "isatty()" here because
+	// "podman run -it" will not give us a full terminal to
+	// prevent TIOCSTI - this is the next best we can do.
+	for _, env := range []string{"TERM", "SSH_CONNECTION"} {
+		if s := os.Getenv(env); s != "" {
+			return true
+		}
+	}
+	return false
+}
+
 // New creates a new progressbar based on the requested type
 func New(typ string) (ProgressBar, error) {
 	switch typ {
-	// XXX: autoseelct based on PS1 value (i.e. use term in
-	// interactive shells only?)
-	case "", "plain":
+	case "":
+		// autoselect based on if we are on an interactive
+		// terminal, use plain progress for scripts
+		if isTerminal() {
+			return NewTerminalProgressBar()
+		}
+		return NewPlainProgressBar()
+	case "plain":
 		return NewPlainProgressBar()
 	case "term":
 		return NewTerminalProgressBar()

bib/internal/progress/progress_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -111,3 +112,27 @@ func TestTermProgress(t *testing.T) {
 	// check shutdown
 	assert.Contains(t, buf.String(), progress.CURSOR_SHOW)
 }
+
+func TestProgressNewAutoselect(t *testing.T) {
+	for _, tc := range []struct {
+		env      string
+		expected interface{}
+	}{
+		{"", &progress.PlainProgressBar{}},
+		{"TERM=vt100", &progress.TerminalProgressBar{}},
+		{"SSH_CONNECTION=totally", &progress.TerminalProgressBar{}},
+	} {
+
+		t.Setenv("TERM", "")
+		t.Setenv("SSH_CONNECTION", "")
+
+		if l := strings.SplitN(tc.env, "=", 2); len(l) == 2 {
+			t.Setenv(l[0], l[1])
+		}
+
+		pb, err := progress.New("")
+		assert.NoError(t, err)
+		assert.Equal(t, reflect.TypeOf(pb), reflect.TypeOf(tc.expected), fmt.Sprintf("[%v] %T not the expected %T", tc.env, pb, tc.expected))
+	}
+
+}