fix: use StringArrayVar to parse http header

StringSliceVar will separated by comma, which is not suitable for field
like Date:Mon, 30 Dec 2019, use StringArrayVar instead

Signed-off-by: 慕陶 <jihui.xjh@antfin.com>

cmd/dfget/app/root.go

@@ -238,7 +238,7 @@ func initFlags() {
 		"filter some query params of URL, use char '&' to separate different params"+
 			"\neg: -f 'key&sign' will filter 'key' and 'sign' query param"+
 			"\nin this way, different but actually the same URLs can reuse the same downloading task")
-	flagSet.StringSliceVar(&cfg.Header, "header", nil,
+	flagSet.StringArrayVar(&cfg.Header, "header", nil,
 		"http header, eg: --header='Accept: *' --header='Host: abc'")
 	flagSet.VarP(config.NewSupernodesValue(&cfg.Supernodes, nil), "node", "n",
 		"specify the addresses(host:port=weight) of supernodes where the host is necessary, the port(default: 8002) and the weight(default:1) are optional. And the type of weight must be integer")

cmd/dfget/app/root_test.go

@@ -27,6 +27,7 @@ import (
 	"github.com/dragonflyoss/Dragonfly/dfget/config"
 	"github.com/dragonflyoss/Dragonfly/pkg/errortypes"
 	"github.com/dragonflyoss/Dragonfly/pkg/rate"
+
 	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/suite"
 )
@@ -91,6 +92,17 @@ func (suit *dfgetSuit) Test_initProperties() {
 	}
 }
 
+func (suit *dfgetSuit) Test_HeaderFlags() {
+	originCfg := *cfg
+	defer func() {
+		cfg = &originCfg
+	}()
+	flagSet := rootCmd.Flags()
+	flagSet.Parse([]string{"--header", "Host: abc", "--header", "Date:Mon, 30 Dec 2019"})
+
+	suit.Equal(cfg.Header, []string{"Host: abc", "Date:Mon, 30 Dec 2019"})
+}
+
 func (suit *dfgetSuit) Test_transFilter() {
 	var cases = []string{
 		"a&b&c",