capability: support empty input on Decode. (#153)

Calling capability.List's Decode with nil input will have no effect.
This is useful in other decoders, where an empty capability list is
received as an empty byte slice.

2 files changed, 11 insertions, 0 deletions

diff --git a/plumbing/protocol/packp/capability/list.go b/plumbing/protocol/packp/capability/list.go
index 73d1f25..ff8d4a4 100644
--- a/plumbing/protocol/packp/capability/list.go
+++ b/plumbing/protocol/packp/capability/list.go
@@ -48,6 +48,10 @@ func (l *List) IsEmpty() bool {
 
 // Decode decodes list of capabilities from raw into the list
 func (l *List) Decode(raw []byte) error {
+	if len(raw) == 0 {
+		return nil
+	}
+
 	for _, data := range bytes.Split(raw, []byte{' '}) {
 		pair := bytes.SplitN(data, []byte{'='}, 2)
 
diff --git a/plumbing/protocol/packp/capability/list_test.go b/plumbing/protocol/packp/capability/list_test.go
index 6d350b0..eeb3173 100644
--- a/plumbing/protocol/packp/capability/list_test.go
+++ b/plumbing/protocol/packp/capability/list_test.go
@@ -27,6 +27,13 @@ func (s *SuiteCapabilities) TestDecode(c *check.C) {
 	c.Assert(cap.Get(ThinPack), check.IsNil)
 }
 
+func (s *SuiteCapabilities) TestDecodeEmpty(c *check.C) {
+	cap := NewList()
+	err := cap.Decode(nil)
+	c.Assert(err, check.IsNil)
+	c.Assert(cap, check.DeepEquals, NewList())
+}
+
 func (s *SuiteCapabilities) TestDecodeWithErrArguments(c *check.C) {
 	cap := NewList()
 	err := cap.Decode([]byte("thin-pack=foo"))