// This does not cover STAR extensions to the PAX format; these fall under
	// the PAX format.
	formatSTAR

	formatMax
)

func (f Format) has(f2 Format) bool   { return f&f2 != 0 }
func (f *Format) mayBe(f2 Format)     { *f |= f2 }
func (f *Format) mayOnlyBe(f2 Format) { *f &= f2 }
func (f *Format) mustNotBe(f2 Format) { *f &^= f2 }

var formatNames = map[Format]string{

			format.mustNotBe(FormatUSTAR)
		}
	*/

	// Check desired format.
	if wantFormat := h.Format; wantFormat != FormatUnknown {
		if wantFormat.has(FormatPAX) && !preferPAX {
			wantFormat.mayBe(FormatUSTAR) // PAX implies USTAR allowed too
		}
		format.mayOnlyBe(wantFormat) // Set union of formats allowed and format wanted
	}
	if format == FormatUnknown {
		switch h.Format {
		case FormatUSTAR: