Use advrefs in gituploadpackinfo (#92)

* add advrefs encoder and parser

* modify advrefs encoder to resemble json encoder

* turn advrefs parser into a decoder

* clean code

* improve documentation

* improve documentation

* clean code

* upgrade to new pktline.Add and add Flush const to easy integration

* gometalinter

* Use packp/advrefs for GitUploadPackInfo parsing

- GitUploadPackInfo now uses packp/advrefs instead of parsing the
  message by itself.

- Capabilities has been moved from clients/common to packp to avoid a
  circular import.

- Cleaning of advrefs_test code.

- Add support for prefix encoding and decoding in advrefs.

* clean advrefs test code

* clean advrefs test code

* clean advrefs test code

* gometalinter

* add pktline encoder

* change pktline.EncodeFlush to pktline.Flush

* make scanner tests use the encoder instead of Pktlines

* check errors on flush and clean constants

* ubstitute the PktLines type with a pktline.Encoder

* use pktline.Encoder in all go-git

* add example of pktline.Encodef()

* add package overview

* documentation

* support symbolic links other than HEAD

* simplify decoding of shallows

* packp: fix mcuadros comments

- all abbreviates removed (by visual inspection, some may remain)
- all empty maps are initialized using make
- simplify readRef with a switch
- make decodeShallow malformed error more verbose
- add pktline.Encoder.encodeLine
- remove infamous panic in checkPayloadLength by refactoring out
  the whole function

1 files changed, 249 insertions, 0 deletions

diff --git a/formats/packp/pktline/encoder_test.go b/formats/packp/pktline/encoder_test.go
new file mode 100644
index 0000000..5990ea5
--- /dev/null
+++ b/formats/packp/pktline/encoder_test.go
@@ -0,0 +1,249 @@
+package pktline_test
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"testing"
+
+	"gopkg.in/src-d/go-git.v4/formats/packp/pktline"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type SuiteEncoder struct{}
+
+var _ = Suite(&SuiteEncoder{})
+
+func (s *SuiteEncoder) TestFlush(c *C) {
+	var buf bytes.Buffer
+	e := pktline.NewEncoder(&buf)
+
+	err := e.Flush()
+	c.Assert(err, IsNil)
+
+	obtained := buf.Bytes()
+	c.Assert(obtained, DeepEquals, pktline.FlushPkt)
+}
+
+func (s *SuiteEncoder) TestEncode(c *C) {
+	for i, test := range [...]struct {
+		input    [][]byte
+		expected []byte
+	}{
+		{
+			input: [][]byte{
+				[]byte("hello\n"),
+			},
+			expected: []byte("000ahello\n"),
+		}, {
+			input: [][]byte{
+				[]byte("hello\n"),
+				pktline.Flush,
+			},
+			expected: []byte("000ahello\n0000"),
+		}, {
+			input: [][]byte{
+				[]byte("hello\n"),
+				[]byte("world!\n"),
+				[]byte("foo"),
+			},
+			expected: []byte("000ahello\n000bworld!\n0007foo"),
+		}, {
+			input: [][]byte{
+				[]byte("hello\n"),
+				pktline.Flush,
+				[]byte("world!\n"),
+				[]byte("foo"),
+				pktline.Flush,
+			},
+			expected: []byte("000ahello\n0000000bworld!\n0007foo0000"),
+		}, {
+			input: [][]byte{
+				[]byte(strings.Repeat("a", pktline.MaxPayloadSize)),
+			},
+			expected: []byte(
+				"fff0" + strings.Repeat("a", pktline.MaxPayloadSize)),
+		}, {
+			input: [][]byte{
+				[]byte(strings.Repeat("a", pktline.MaxPayloadSize)),
+				[]byte(strings.Repeat("b", pktline.MaxPayloadSize)),
+			},
+			expected: []byte(
+				"fff0" + strings.Repeat("a", pktline.MaxPayloadSize) +
+					"fff0" + strings.Repeat("b", pktline.MaxPayloadSize)),
+		},
+	} {
+		comment := Commentf("input %d = %v\n", i, test.input)
+
+		var buf bytes.Buffer
+		e := pktline.NewEncoder(&buf)
+
+		err := e.Encode(test.input...)
+		c.Assert(err, IsNil, comment)
+
+		c.Assert(buf.Bytes(), DeepEquals, test.expected, comment)
+	}
+}
+
+func (s *SuiteEncoder) TestEncodeErrPayloadTooLong(c *C) {
+	for i, input := range [...][][]byte{
+		[][]byte{
+			[]byte(strings.Repeat("a", pktline.MaxPayloadSize+1)),
+		},
+		[][]byte{
+			[]byte("hello world!"),
+			[]byte(strings.Repeat("a", pktline.MaxPayloadSize+1)),
+		},
+		[][]byte{
+			[]byte("hello world!"),
+			[]byte(strings.Repeat("a", pktline.MaxPayloadSize+1)),
+			[]byte("foo"),
+		},
+	} {
+		comment := Commentf("input %d = %v\n", i, input)
+
+		var buf bytes.Buffer
+		e := pktline.NewEncoder(&buf)
+
+		err := e.Encode(input...)
+		c.Assert(err, Equals, pktline.ErrPayloadTooLong, comment)
+	}
+}
+
+func (s *SuiteEncoder) TestEncodeStrings(c *C) {
+	for i, test := range [...]struct {
+		input    []string
+		expected []byte
+	}{
+		{
+			input: []string{
+				"hello\n",
+			},
+			expected: []byte("000ahello\n"),
+		}, {
+			input: []string{
+				"hello\n",
+				pktline.FlushString,
+			},
+			expected: []byte("000ahello\n0000"),
+		}, {
+			input: []string{
+				"hello\n",
+				"world!\n",
+				"foo",
+			},
+			expected: []byte("000ahello\n000bworld!\n0007foo"),
+		}, {
+			input: []string{
+				"hello\n",
+				pktline.FlushString,
+				"world!\n",
+				"foo",
+				pktline.FlushString,
+			},
+			expected: []byte("000ahello\n0000000bworld!\n0007foo0000"),
+		}, {
+			input: []string{
+				strings.Repeat("a", pktline.MaxPayloadSize),
+			},
+			expected: []byte(
+				"fff0" + strings.Repeat("a", pktline.MaxPayloadSize)),
+		}, {
+			input: []string{
+				strings.Repeat("a", pktline.MaxPayloadSize),
+				strings.Repeat("b", pktline.MaxPayloadSize),
+			},
+			expected: []byte(
+				"fff0" + strings.Repeat("a", pktline.MaxPayloadSize) +
+					"fff0" + strings.Repeat("b", pktline.MaxPayloadSize)),
+		},
+	} {
+		comment := Commentf("input %d = %v\n", i, test.input)
+
+		var buf bytes.Buffer
+		e := pktline.NewEncoder(&buf)
+
+		err := e.EncodeString(test.input...)
+		c.Assert(err, IsNil, comment)
+		c.Assert(buf.Bytes(), DeepEquals, test.expected, comment)
+	}
+}
+
+func (s *SuiteEncoder) TestEncodeStringErrPayloadTooLong(c *C) {
+	for i, input := range [...][]string{
+		[]string{
+			strings.Repeat("a", pktline.MaxPayloadSize+1),
+		},
+		[]string{
+			"hello world!",
+			strings.Repeat("a", pktline.MaxPayloadSize+1),
+		},
+		[]string{
+			"hello world!",
+			strings.Repeat("a", pktline.MaxPayloadSize+1),
+			"foo",
+		},
+	} {
+		comment := Commentf("input %d = %v\n", i, input)
+
+		var buf bytes.Buffer
+		e := pktline.NewEncoder(&buf)
+
+		err := e.EncodeString(input...)
+		c.Assert(err, Equals, pktline.ErrPayloadTooLong, comment)
+	}
+}
+
+func (s *SuiteEncoder) TestEncodef(c *C) {
+	format := " %s %d\n"
+	str := "foo"
+	d := 42
+
+	var buf bytes.Buffer
+	e := pktline.NewEncoder(&buf)
+
+	err := e.Encodef(format, str, d)
+	c.Assert(err, IsNil)
+
+	expected := []byte("000c foo 42\n")
+	c.Assert(buf.Bytes(), DeepEquals, expected)
+}
+
+func ExampleEncoder() {
+	// Create an encoder that writes pktlines to stdout.
+	e := pktline.NewEncoder(os.Stdout)
+
+	// Encode some data as a new pkt-line.
+	_ = e.Encode([]byte("data\n")) // error checks removed for brevity
+
+	// Encode a flush-pkt.
+	_ = e.Flush()
+
+	// Encode a couple of byte slices and a flush in one go. Each of
+	// them will end up as payloads of their own pktlines.
+	_ = e.Encode(
+		[]byte("hello\n"),
+		[]byte("world!\n"),
+		pktline.Flush,
+	)
+
+	// You can also encode strings:
+	_ = e.EncodeString(
+		"foo\n",
+		"bar\n",
+		pktline.FlushString,
+	)
+
+	// You can also format and encode a payload:
+	_ = e.Encodef(" %s %d\n", "foo", 42)
+	// Output:
+	// 0009data
+	// 0000000ahello
+	// 000bworld!
+	// 00000008foo
+	// 0008bar
+	// 0000000c foo 42
+}