Add --phony option for disabling search

With --phony, fzf becomes a simply selector interface without its own
search functionality. The query string is only used for building the
command for preview or execute action.

Close #1723

src/core.go

@@ -227,6 +227,12 @@ func Run(opts *Options, revision string) {
 	for {
 		delay := true
 		ticks++
+		input := func() []rune {
+			if opts.Phony {
+				return []rune{}
+			}
+			return []rune(terminal.Input())
+		}
 		eventBox.Wait(func(events *util.Events) {
 			if _, fin := (*events)[EvtReadFin]; fin {
 				delete(*events, EvtReadNew)
@@ -241,7 +247,7 @@ func Run(opts *Options, revision string) {
 					if opts.Sync {
 						terminal.UpdateList(PassMerger(&snapshot, opts.Tac))
 					}
-					matcher.Reset(snapshot, terminal.Input(), false, !reading, sort)
+					matcher.Reset(snapshot, input(), false, !reading, sort)
 
 				case EvtSearchNew:
 					switch val := value.(type) {
@@ -249,7 +255,7 @@ func Run(opts *Options, revision string) {
 						sort = val
 					}
 					snapshot, _ := chunkList.Snapshot()
-					matcher.Reset(snapshot, terminal.Input(), true, !reading, sort)
+					matcher.Reset(snapshot, input(), true, !reading, sort)
 					delay = false
 
 				case EvtSearchProgress:

src/options.go

@@ -33,6 +33,7 @@ const usage = `usage: fzf [options]
     -d, --delimiter=STR   Field delimiter regex (default: AWK-style)
     +s, --no-sort         Do not sort the result
     --tac                 Reverse the order of the input
+    --phony               Do not perform search
     --tiebreak=CRI[,..]   Comma-separated list of sort criteria to apply
                           when the scores are tied [length|begin|end|index]
                           (default: length)
@@ -154,6 +155,7 @@ type Options struct {
 	Fuzzy       bool
 	FuzzyAlgo   algo.Algo
 	Extended    bool
+	Phony       bool
 	Case        Case
 	Normalize   bool
 	Nth         []Range
@@ -207,6 +209,7 @@ func defaultOptions() *Options {
 		Fuzzy:       true,
 		FuzzyAlgo:   algo.FuzzyMatchV2,
 		Extended:    true,
+		Phony:       false,
 		Case:        CaseSmart,
 		Normalize:   true,
 		Nth:         make([]Range, 0),
@@ -1014,6 +1017,10 @@ func parseOptions(opts *Options, allArgs []string) {
 			}
 		case "--no-expect":
 			opts.Expect = make(map[int]string)
+		case "--no-phony":
+			opts.Phony = false
+		case "--phony":
+			opts.Phony = true
 		case "--tiebreak":
 			opts.Criteria = parseTiebreak(nextString(allArgs, &i, "sort criterion required"))
 		case "--bind":