consolidate checks whether stdin/stdout is terminal

internal/terminal/stdio.go

@@ -0,0 +1,29 @@
+package terminal
+
+import (
+	"os"
+
+	"golang.org/x/term"
+)
+
+func StdinIsTerminal() bool {
+	return term.IsTerminal(int(os.Stdin.Fd()))
+}
+
+func StdoutIsTerminal() bool {
+	// mintty on windows can use pipes which behave like a posix terminal,
+	// but which are not a terminal handle
+	return term.IsTerminal(int(os.Stdout.Fd())) || StdoutCanUpdateStatus()
+}
+
+func StdoutCanUpdateStatus() bool {
+	return CanUpdateStatus(os.Stdout.Fd())
+}
+
+func StdoutTerminalWidth() int {
+	w, _, err := term.GetSize(int(os.Stdout.Fd()))
+	if err != nil {
+		return 0
+	}
+	return w
+}