fs/hash: move interface assertion to tests so it doesn't pull in spf13/flag

fs/hash/hash.go

@@ -11,7 +11,6 @@ import (
 
 	"github.com/ncw/rclone/backend/dropbox/dbhash"
 	"github.com/pkg/errors"
-	"github.com/spf13/pflag"
 )
 
 // Type indicates a standard hashing algorithm
@@ -110,9 +109,6 @@ func (h Type) Type() string {
 	return "string"
 }
 
-// Check it satisfies the interface
-var _ pflag.Value = (*Type)(nil)
-
 // fromTypes will return hashers for all the requested types.
 // The types must be a subset of SupportedHashes,
 // and this function must support all types.

fs/hash/hash_test.go

@@ -6,10 +6,14 @@ import (
 	"testing"
 
 	"github.com/ncw/rclone/fs/hash"
+	"github.com/spf13/pflag"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+// Check it satisfies the interface
+var _ pflag.Value = (*hash.Type)(nil)
+
 func TestHashSet(t *testing.T) {
 	var h hash.Set