plumbing: handle pktline erro-line as errors

Error when encountering an error-line
See https://git-scm.com/docs/pack-protocol

Update plumbing/format/pktline/error.go

Co-authored-by: Paulo Gomes <paulo.gomes.uk@gmail.com>

Update plumbing/format/pktline/error.go

Co-authored-by: Paulo Gomes <paulo.gomes.uk@gmail.com>

feat: format newline

1 files changed, 51 insertions, 0 deletions

diff --git a/plumbing/format/pktline/error.go b/plumbing/format/pktline/error.go
new file mode 100644
index 0000000..2c0e5a7
--- /dev/null
+++ b/plumbing/format/pktline/error.go
@@ -0,0 +1,51 @@
+package pktline
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"strings"
+)
+
+var (
+	// ErrInvalidErrorLine is returned by Decode when the packet line is not an
+	// error line.
+	ErrInvalidErrorLine = errors.New("expected an error-line")
+
+	errPrefix = []byte("ERR ")
+)
+
+// ErrorLine is a packet line that contains an error message.
+// Once this packet is sent by client or server, the data transfer process is
+// terminated.
+// See https://git-scm.com/docs/pack-protocol#_pkt_line_format
+type ErrorLine struct {
+	Text string
+}
+
+// Error implements the error interface.
+func (e *ErrorLine) Error() string {
+	return e.Text
+}
+
+// Encode encodes the ErrorLine into a packet line.
+func (e *ErrorLine) Encode(w io.Writer) error {
+	p := NewEncoder(w)
+	return p.Encodef("%s%s\n", string(errPrefix), e.Text)
+}
+
+// Decode decodes a packet line into an ErrorLine.
+func (e *ErrorLine) Decode(r io.Reader) error {
+	s := NewScanner(r)
+	if !s.Scan() {
+		return s.Err()
+	}
+
+	line := s.Bytes()
+	if !bytes.HasPrefix(line, errPrefix) {
+		return ErrInvalidErrorLine
+	}
+
+	e.Text = strings.TrimSpace(string(line[4:]))
+	return nil
+}