cmp/report_slices.go
func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStats {
	groups, groupsOrig := groups[:0], groups
	for i, ds := range groupsOrig {
		if len(groups) >= 2 && ds.NumDiff() > 0 {
			prev := &groups[len(groups)-2] // Unequal group
			curr := &groups[len(groups)-1] // Equal group
			next := &groupsOrig[i]         // Unequal group
			hadX, hadY := prev.NumRemoved > 0, prev.NumInserted > 0
			hasX, hasY := next.NumRemoved > 0, next.NumInserted > 0
			if ((hadX || hasX) && (hadY || hasY)) && curr.NumIdentical <= windowSize {
				*prev = (*prev).Append(*curr).Append(*next)
				groups = groups[:len(groups)-1] // Truncate off equal group
				continue
			}
		}
		groups = append(groups, ds)
	}
	return groups
}
func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStats {
	groups, groupsOrig := groups[:0], groups
	for i, ds := range groupsOrig {
		if len(groups) >= 2 && ds.NumDiff() > 0 {
			prev := &groups[len(groups)-2] // Unequal group
			curr := &groups[len(groups)-1] // Equal group
			next := &groupsOrig[i]         // Unequal group
			hadX, hadY := prev.NumRemoved > 0, prev.NumInserted > 0
			hasX, hasY := next.NumRemoved > 0, next.NumInserted > 0
			if ((hadX || hasX) && (hadY || hasY)) && curr.NumIdentical <= windowSize {
				*prev = (*prev).Append(*curr).Append(*next)
				groups = groups[:len(groups)-1] // Truncate off equal group
				continue
			}
		}
		groups = append(groups, ds)
	}
	return groups
}
// coalesceInterveningIdentical coalesces sufficiently short (<= windowSize)
// equal groups into adjacent unequal groups that currently result in a
// dual inserted/removed printout. This acts as a high-pass filter to smooth
// out high-frequency changes within the windowSize.