Consolidate Result and rank structs

By not storing item index twice, we can cut down the size of Result
struct and now it makes more sense to store and pass Results by values.
Benchmarks show no degradation of performance by additional pointer
indirection for looking up index.

src/merger.go

@@ -3,14 +3,14 @@ package fzf
 import "fmt"
 
 // EmptyMerger is a Merger with no data
-var EmptyMerger = NewMerger(nil, [][]*Result{}, false, false)
+var EmptyMerger = NewMerger(nil, [][]Result{}, false, false)
 
 // Merger holds a set of locally sorted lists of items and provides the view of
 // a single, globally-sorted list
 type Merger struct {
 	pattern *Pattern
-	lists   [][]*Result
-	merged  []*Result
+	lists   [][]Result
+	merged  []Result
 	chunks  *[]*Chunk
 	cursors []int
 	sorted  bool
@@ -35,11 +35,11 @@ func PassMerger(chunks *[]*Chunk, tac bool) *Merger {
 }
 
 // NewMerger returns a new Merger
-func NewMerger(pattern *Pattern, lists [][]*Result, sorted bool, tac bool) *Merger {
+func NewMerger(pattern *Pattern, lists [][]Result, sorted bool, tac bool) *Merger {
 	mg := Merger{
 		pattern: pattern,
 		lists:   lists,
-		merged:  []*Result{},
+		merged:  []Result{},
 		chunks:  nil,
 		cursors: make([]int, len(lists)),
 		sorted:  sorted,
@@ -59,13 +59,13 @@ func (mg *Merger) Length() int {
 }
 
 // Get returns the pointer to the Result object indexed by the given integer
-func (mg *Merger) Get(idx int) *Result {
+func (mg *Merger) Get(idx int) Result {
 	if mg.chunks != nil {
 		if mg.tac {
 			idx = mg.count - idx - 1
 		}
 		chunk := (*mg.chunks)[idx/chunkSize]
-		return &Result{item: &(*chunk)[idx%chunkSize]}
+		return Result{item: &(*chunk)[idx%chunkSize]}
 	}
 
 	if mg.sorted {
@@ -89,7 +89,7 @@ func (mg *Merger) cacheable() bool {
 	return mg.count < mergerCacheMax
 }
 
-func (mg *Merger) mergedGet(idx int) *Result {
+func (mg *Merger) mergedGet(idx int) Result {
 	for i := len(mg.merged); i <= idx; i++ {
 		minRank := minRank()
 		minIdx := -1
@@ -100,7 +100,7 @@ func (mg *Merger) mergedGet(idx int) *Result {
 				continue
 			}
 			if cursor >= 0 {
-				rank := list[cursor].rank
+				rank := list[cursor]
 				if minIdx < 0 || compareRanks(rank, minRank, mg.tac) {
 					minRank = rank
 					minIdx = listIdx