fs: add --all to rclone config create/update to ask all the config questions #3455

This also factors the config questions into a state based mechanism so
a backend can be configured using the same dialog as rclone config but
remotely.

fs/backend_config_test.go

@@ -1,6 +1,7 @@
 package fs
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -35,3 +36,24 @@ func TestStatePop(t *testing.T) {
 	assert.Equal(t, "1,2,3", value)
 	assert.Equal(t, "a", state)
 }
+
+func TestMatchProvider(t *testing.T) {
+	for _, test := range []struct {
+		config   string
+		provider string
+		want     bool
+	}{
+		{"", "", true},
+		{"one", "one", true},
+		{"one,two", "two", true},
+		{"one,two,three", "two", true},
+		{"one", "on", false},
+		{"one,two,three", "tw", false},
+		{"!one,two,three", "two", false},
+		{"!one,two,three", "four", true},
+	} {
+		what := fmt.Sprintf("%q,%q", test.config, test.provider)
+		got := MatchProvider(test.config, test.provider)
+		assert.Equal(t, test.want, got, what)
+	}
+}