Add --with-shell for shelling out with different command and flags (#3746)

Close #3732

src/terminal_unix.go

@@ -5,26 +5,11 @@ package fzf
 import (
 	"os"
 	"os/signal"
-	"strings"
 	"syscall"
 
 	"golang.org/x/sys/unix"
 )
 
-var escaper *strings.Replacer
-
-func init() {
-	tokens := strings.Split(os.Getenv("SHELL"), "/")
-	if tokens[len(tokens)-1] == "fish" {
-		// https://fishshell.com/docs/current/language.html#quotes
-		// > The only meaningful escape sequences in single quotes are \', which
-		// > escapes a single quote and \\, which escapes the backslash symbol.
-		escaper = strings.NewReplacer("\\", "\\\\", "'", "\\'")
-	} else {
-		escaper = strings.NewReplacer("'", "'\\''")
-	}
-}
-
 func notifyOnResize(resizeChan chan<- os.Signal) {
 	signal.Notify(resizeChan, syscall.SIGWINCH)
 }
@@ -41,7 +26,3 @@ func notifyStop(p *os.Process) {
 func notifyOnCont(resizeChan chan<- os.Signal) {
 	signal.Notify(resizeChan, syscall.SIGCONT)
 }
-
-func quoteEntry(entry string) string {
-	return "'" + escaper.Replace(entry) + "'"
-}