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

Close #3732

src/util/util_unix.go

@@ -3,31 +3,71 @@
 package util
 
 import (
+	"fmt"
 	"os"
 	"os/exec"
+	"strings"
 	"syscall"
 
 	"golang.org/x/sys/unix"
 )
 
-// ExecCommand executes the given command with $SHELL
-func ExecCommand(command string, setpgid bool) *exec.Cmd {
-	shell := os.Getenv("SHELL")
-	if len(shell) == 0 {
-		shell = "sh"
-	}
-	return ExecCommandWith(shell, command, setpgid)
+type Executor struct {
+	shell   string
+	args    []string
+	escaper *strings.Replacer
 }
 
-// ExecCommandWith executes the given command with the specified shell
-func ExecCommandWith(shell string, command string, setpgid bool) *exec.Cmd {
-	cmd := exec.Command(shell, "-c", command)
+func NewExecutor(withShell string) *Executor {
+	shell := os.Getenv("SHELL")
+	args := strings.Fields(withShell)
+	if len(args) > 0 {
+		shell = args[0]
+		args = args[1:]
+	} else {
+		if len(shell) == 0 {
+			shell = "sh"
+		}
+		args = []string{"-c"}
+	}
+
+	var escaper *strings.Replacer
+	tokens := strings.Split(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("'", "'\\''")
+	}
+	return &Executor{shell, args, escaper}
+}
+
+// ExecCommand executes the given command with $SHELL
+func (x *Executor) ExecCommand(command string, setpgid bool) *exec.Cmd {
+	cmd := exec.Command(x.shell, append(x.args, command)...)
 	if setpgid {
 		cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
 	}
 	return cmd
 }
 
+func (x *Executor) QuoteEntry(entry string) string {
+	return "'" + x.escaper.Replace(entry) + "'"
+}
+
+func (x *Executor) Become(stdin *os.File, environ []string, command string) {
+	shellPath, err := exec.LookPath(x.shell)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "fzf (become): %s\n", err.Error())
+		Exit(127)
+	}
+	args := append([]string{shellPath}, append(x.args, command)...)
+	SetStdin(stdin)
+	syscall.Exec(shellPath, args, environ)
+}
+
 // KillCommand kills the process for the given command
 func KillCommand(cmd *exec.Cmd) error {
 	return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)