remote: add Push (#178)

* remote: add Push.

* add Push method to Remote.
* add method Push to Repository.
* examples: add push example.

* requested changes

* add tests, fixes

2 files changed, 33 insertions, 15 deletions

diff --git a/plumbing/protocol/packp/report_status.go b/plumbing/protocol/packp/report_status.go
index ead4bb6..29c1a4c 100644
--- a/plumbing/protocol/packp/report_status.go
+++ b/plumbing/protocol/packp/report_status.go
@@ -26,9 +26,19 @@ func NewReportStatus() *ReportStatus {
 	return &ReportStatus{}
 }
 
-// Ok returns true if the report status reported no error.
-func (s *ReportStatus) Ok() bool {
-	return s.UnpackStatus == ok
+// Error returns the first error if any.
+func (s *ReportStatus) Error() error {
+	if s.UnpackStatus != ok {
+		return fmt.Errorf("unpack error: %s", s.UnpackStatus)
+	}
+
+	for _, s := range s.CommandStatuses {
+		if err := s.Error(); err != nil {
+			return err
+		}
+	}
+
+	return nil
 }
 
 // Encode writes the report status to a writer.
@@ -135,14 +145,19 @@ type CommandStatus struct {
 	Status        string
 }
 
-// Ok returns true if the command status reported no error.
-func (s *CommandStatus) Ok() bool {
-	return s.Status == ok
+// Error returns the error, if any.
+func (s *CommandStatus) Error() error {
+	if s.Status == ok {
+		return nil
+	}
+
+	return fmt.Errorf("command error on %s: %s",
+		s.ReferenceName.String(), s.Status)
 }
 
 func (s *CommandStatus) encode(w io.Writer) error {
 	e := pktline.NewEncoder(w)
-	if s.Ok() {
+	if s.Error() == nil {
 		return e.Encodef("ok %s\n", s.ReferenceName.String())
 	}
 
diff --git a/plumbing/protocol/packp/report_status_test.go b/plumbing/protocol/packp/report_status_test.go
index 168d25b..1c3fa81 100644
--- a/plumbing/protocol/packp/report_status_test.go
+++ b/plumbing/protocol/packp/report_status_test.go
@@ -13,22 +13,25 @@ type ReportStatusSuite struct{}
 
 var _ = Suite(&ReportStatusSuite{})
 
-func (s *ReportStatusSuite) TestOk(c *C) {
+func (s *ReportStatusSuite) TestError(c *C) {
 	rs := NewReportStatus()
 	rs.UnpackStatus = "ok"
-	c.Assert(rs.Ok(), Equals, true)
+	c.Assert(rs.Error(), IsNil)
 	rs.UnpackStatus = "OK"
-	c.Assert(rs.Ok(), Equals, false)
+	c.Assert(rs.Error(), ErrorMatches, "unpack error: OK")
 	rs.UnpackStatus = ""
-	c.Assert(rs.Ok(), Equals, false)
+	c.Assert(rs.Error(), ErrorMatches, "unpack error: ")
+
+	cs := &CommandStatus{ReferenceName: plumbing.ReferenceName("ref")}
+	rs.UnpackStatus = "ok"
+	rs.CommandStatuses = append(rs.CommandStatuses, cs)
 
-	cs := &CommandStatus{}
 	cs.Status = "ok"
-	c.Assert(cs.Ok(), Equals, true)
+	c.Assert(rs.Error(), IsNil)
 	cs.Status = "OK"
-	c.Assert(cs.Ok(), Equals, false)
+	c.Assert(rs.Error(), ErrorMatches, "command error on ref: OK")
 	cs.Status = ""
-	c.Assert(cs.Ok(), Equals, false)
+	c.Assert(rs.Error(), ErrorMatches, "command error on ref: ")
 }
 
 func (s *ReportStatusSuite) testEncodeDecodeOk(c *C, rs *ReportStatus, lines ...string) {