Quote rc commands if necessary

Surround an argument with quotes before assembling it into a command
base on whether a command requires quoting to be parsed by rc as it
was received through args. If the arg contains any of rc's special
characters or whitespace as documented in rc(1), it is quoted and
any ' characters are escaped to ''.

The quoted command string is also appended to the dump command.

Fixes #135

Author: cptaffe

acme/Watch/main.go

@@ -47,6 +47,8 @@ import (
 	"9fans.net/go/acme"
 )
 
+const rcspecial = "#;&|^$=`'{}()<> \t\n"
+
 var args []string
 var win *acme.Win
 var needrun = make(chan bool, 1)
@@ -64,6 +66,8 @@ func main() {
 	flag.Parse()
 	args = flag.Args()
 
+	escaped := rcquote(args)
+
 	var err error
 	win, err = acme.New()
 	if err != nil {
@@ -80,7 +84,7 @@ func main() {
 	}
 	win.Ctl(cmd)
 	win.Fprintf("tag", "Get Kill Quit ")
-	win.Fprintf("body", "%% %s\n", strings.Join(args, " "))
+	win.Fprintf("body", "%% %s\n", escaped)
 
 	needrun <- true
 	go events()
@@ -329,3 +333,18 @@ func runBackground(id int, dir string) {
 		// Continue loop with lock held
 	}
 }
+
+func rcquote(args []string) string {
+	var b strings.Builder
+	for i, arg := range args {
+		if i != 0 {
+			b.WriteRune(' ')
+		}
+		if strings.ContainsAny(arg, rcspecial) {
+			fmt.Fprintf(&b, "'%s'", strings.ReplaceAll(arg, "'", "''"))
+		} else {
+			b.WriteString(arg)
+		}
+	}
+	return b.String()
+}