4 files changed, 41 insertions, 12 deletions
diff --git a/plumbing/protocol/packp/srvresp.go b/plumbing/protocol/packp/srvresp.go
index b3a7ee8..8cd0a72 100644
--- a/plumbing/protocol/packp/srvresp.go
+++ b/plumbing/protocol/packp/srvresp.go
@@ -21,11 +21,6 @@ type ServerResponse struct {
 // Decode decodes the response into the struct, isMultiACK should be true, if
 // the request was done with multi_ack or multi_ack_detailed capabilities.
 func (r *ServerResponse) Decode(reader *bufio.Reader, isMultiACK bool) error {
-	// TODO: implement support for multi_ack or multi_ack_detailed responses
-	if isMultiACK {
-		return errors.New("multi_ack and multi_ack_detailed are not supported")
-	}
-
 	s := pktline.NewScanner(reader)
 
 	for s.Scan() {
@@ -48,7 +43,23 @@ func (r *ServerResponse) Decode(reader *bufio.Reader, isMultiACK bool) error {
 		}
 	}
 
-	return s.Err()
+	// isMultiACK is true when the remote server advertises the related
+	// capabilities when they are not in transport.UnsupportedCapabilities.
+	//
+	// Users may decide to remove multi_ack and multi_ack_detailed from the
+	// unsupported capabilities list, which allows them to do initial clones
+	// from Azure DevOps.
+	//
+	// Follow-up fetches may error, therefore errors are wrapped with additional
+	// information highlighting that this capabilities are not supported by go-git.
+	//
+	// TODO: Implement support for multi_ack or multi_ack_detailed responses.
+	err := s.Err()
+	if err != nil && isMultiACK {
+		return fmt.Errorf("multi_ack and multi_ack_detailed are not supported: %w", err)
+	}
+
+	return err
 }
 
 // stopReading detects when a valid command such as ACK or NAK is found to be
@@ -113,8 +124,9 @@ func (r *ServerResponse) decodeACKLine(line []byte) error {
 }
 
 // Encode encodes the ServerResponse into a writer.
-func (r *ServerResponse) Encode(w io.Writer) error {
-	if len(r.ACKs) > 1 {
+func (r *ServerResponse) Encode(w io.Writer, isMultiACK bool) error {
+	if len(r.ACKs) > 1 && !isMultiACK {
+		// For further information, refer to comments in the Decode func above.
 		return errors.New("multi_ack and multi_ack_detailed are not supported")
 	}
 
diff --git a/plumbing/protocol/packp/srvresp_test.go b/plumbing/protocol/packp/srvresp_test.go
index 02fab42..aa0af52 100644
--- a/plumbing/protocol/packp/srvresp_test.go
+++ b/plumbing/protocol/packp/srvresp_test.go
@@ -72,8 +72,21 @@ func (s *ServerResponseSuite) TestDecodeMalformed(c *C) {
 	c.Assert(err, NotNil)
 }
 
+// multi_ack isn't fully implemented, this ensures that Decode ignores that fact,
+// as in some circumstances that's OK to assume so.
+//
+// TODO: Review as part of multi_ack implementation.
 func (s *ServerResponseSuite) TestDecodeMultiACK(c *C) {
+	raw := "" +
+		"0031ACK 1111111111111111111111111111111111111111\n" +
+		"0031ACK 6ecf0ef2c2dffb796033e5a02219af86ec6584e5\n" +
+		"00080PACK\n"
+
 	sr := &ServerResponse{}
-	err := sr.Decode(bufio.NewReader(bytes.NewBuffer(nil)), true)
-	c.Assert(err, NotNil)
+	err := sr.Decode(bufio.NewReader(bytes.NewBufferString(raw)), true)
+	c.Assert(err, IsNil)
+
+	c.Assert(sr.ACKs, HasLen, 2)
+	c.Assert(sr.ACKs[0], Equals, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	c.Assert(sr.ACKs[1], Equals, plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
 }
diff --git a/plumbing/protocol/packp/uppackresp.go b/plumbing/protocol/packp/uppackresp.go
index 26ae61e..a485cb7 100644
--- a/plumbing/protocol/packp/uppackresp.go
+++ b/plumbing/protocol/packp/uppackresp.go
@@ -78,7 +78,7 @@ func (r *UploadPackResponse) Encode(w io.Writer) (err error) {
 		}
 	}
 
-	if err := r.ServerResponse.Encode(w); err != nil {
+	if err := r.ServerResponse.Encode(w, r.isMultiACK); err != nil {
 		return err
 	}
 
diff --git a/plumbing/protocol/packp/uppackresp_test.go b/plumbing/protocol/packp/uppackresp_test.go
index 260dc57..3f87804 100644
--- a/plumbing/protocol/packp/uppackresp_test.go
+++ b/plumbing/protocol/packp/uppackresp_test.go
@@ -59,6 +59,10 @@ func (s *UploadPackResponseSuite) TestDecodeMalformed(c *C) {
 	c.Assert(err, NotNil)
 }
 
+// multi_ack isn't fully implemented, this ensures that Decode ignores that fact,
+// as in some circumstances that's OK to assume so.
+//
+// TODO: Review as part of multi_ack implementation.
 func (s *UploadPackResponseSuite) TestDecodeMultiACK(c *C) {
 	req := NewUploadPackRequest()
 	req.Capabilities.Set(capability.MultiACK)
@@ -67,7 +71,7 @@ func (s *UploadPackResponseSuite) TestDecodeMultiACK(c *C) {
 	defer res.Close()
 
 	err := res.Decode(ioutil.NopCloser(bytes.NewBuffer(nil)))
-	c.Assert(err, NotNil)
+	c.Assert(err, IsNil)
 }
 
 func (s *UploadPackResponseSuite) TestReadNoDecode(c *C) {