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, 315 insertions, 0 deletions

diff --git a/formats/packp/advrefs/advrefs_test.go b/formats/packp/advrefs/advrefs_test.go
new file mode 100644
index 0000000..6950ba5
--- /dev/null
+++ b/formats/packp/advrefs/advrefs_test.go
@@ -0,0 +1,315 @@
+package advrefs_test
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+	"testing"
+
+	"gopkg.in/src-d/go-git.v4/core"
+	"gopkg.in/src-d/go-git.v4/formats/packp/advrefs"
+	"gopkg.in/src-d/go-git.v4/formats/packp/pktline"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type SuiteDecodeEncode struct{}
+
+var _ = Suite(&SuiteDecodeEncode{})
+
+func (s *SuiteDecodeEncode) test(c *C, in []string, exp []string) {
+	var err error
+	var input io.Reader
+	{
+		var buf bytes.Buffer
+		p := pktline.NewEncoder(&buf)
+		err = p.EncodeString(in...)
+		c.Assert(err, IsNil)
+		input = &buf
+	}
+
+	var expected []byte
+	{
+		var buf bytes.Buffer
+		p := pktline.NewEncoder(&buf)
+		err = p.EncodeString(exp...)
+		c.Assert(err, IsNil)
+
+		expected = buf.Bytes()
+	}
+
+	var obtained []byte
+	{
+		ar := advrefs.New()
+		d := advrefs.NewDecoder(input)
+		err = d.Decode(ar)
+		c.Assert(err, IsNil)
+
+		var buf bytes.Buffer
+		e := advrefs.NewEncoder(&buf)
+		err := e.Encode(ar)
+		c.Assert(err, IsNil)
+
+		obtained = buf.Bytes()
+	}
+
+	c.Assert(obtained, DeepEquals, expected,
+		Commentf("input = %v\nobtained = %q\nexpected = %q\n",
+			in, string(obtained), string(expected)))
+}
+
+func (s *SuiteDecodeEncode) TestNoHead(c *C) {
+	input := []string{
+		"0000000000000000000000000000000000000000 capabilities^{}\x00",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"0000000000000000000000000000000000000000 capabilities^{}\x00\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func (s *SuiteDecodeEncode) TestNoHeadSmart(c *C) {
+	input := []string{
+		"# service=git-upload-pack\n",
+		"0000000000000000000000000000000000000000 capabilities^{}\x00",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"# service=git-upload-pack\n",
+		"0000000000000000000000000000000000000000 capabilities^{}\x00\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func (s *SuiteDecodeEncode) TestNoHeadSmartBug(c *C) {
+	input := []string{
+		"# service=git-upload-pack\n",
+		pktline.FlushString,
+		"0000000000000000000000000000000000000000 capabilities^{}\x00\n",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"# service=git-upload-pack\n",
+		pktline.FlushString,
+		"0000000000000000000000000000000000000000 capabilities^{}\x00\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func (s *SuiteDecodeEncode) TestRefs(c *C) {
+	input := []string{
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00multi_ack ofs-delta symref=HEAD:/refs/heads/master\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func (s *SuiteDecodeEncode) TestPeeled(c *C) {
+	input := []string{
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00multi_ack ofs-delta symref=HEAD:/refs/heads/master\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func (s *SuiteDecodeEncode) TestAll(c *C) {
+	input := []string{
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}",
+		"shallow 1111111111111111111111111111111111111111",
+		"shallow 2222222222222222222222222222222222222222\n",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00multi_ack ofs-delta symref=HEAD:/refs/heads/master\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}\n",
+		"shallow 1111111111111111111111111111111111111111\n",
+		"shallow 2222222222222222222222222222222222222222\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func (s *SuiteDecodeEncode) TestAllSmart(c *C) {
+	input := []string{
+		"# service=git-upload-pack\n",
+		pktline.FlushString,
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}\n",
+		"shallow 1111111111111111111111111111111111111111\n",
+		"shallow 2222222222222222222222222222222222222222\n",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"# service=git-upload-pack\n",
+		pktline.FlushString,
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00multi_ack ofs-delta symref=HEAD:/refs/heads/master\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}\n",
+		"shallow 1111111111111111111111111111111111111111\n",
+		"shallow 2222222222222222222222222222222222222222\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func (s *SuiteDecodeEncode) TestAllSmartBug(c *C) {
+	input := []string{
+		"# service=git-upload-pack\n",
+		pktline.FlushString,
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}\n",
+		"shallow 1111111111111111111111111111111111111111\n",
+		"shallow 2222222222222222222222222222222222222222\n",
+		pktline.FlushString,
+	}
+
+	expected := []string{
+		"# service=git-upload-pack\n",
+		pktline.FlushString,
+		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00multi_ack ofs-delta symref=HEAD:/refs/heads/master\n",
+		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
+		"5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c refs/tags/v2.6.11-tree\n",
+		"c39ae07f393806ccf406ef966e9a15afc43cc36a refs/tags/v2.6.11-tree^{}\n",
+		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
+		"8888888888888888888888888888888888888888 refs/tags/v2.6.12-tree^{}\n",
+		"shallow 1111111111111111111111111111111111111111\n",
+		"shallow 2222222222222222222222222222222222222222\n",
+		pktline.FlushString,
+	}
+
+	s.test(c, input, expected)
+}
+
+func ExampleDecoder_Decode() {
+	// Here is a raw advertised-ref message.
+	raw := "" +
+		"0065a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 HEAD\x00multi_ack ofs-delta symref=HEAD:/refs/heads/master\n" +
+		"003fa6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n" +
+		"00441111111111111111111111111111111111111111 refs/tags/v2.6.11-tree\n" +
+		"00475555555555555555555555555555555555555555 refs/tags/v2.6.11-tree^{}\n" +
+		"0035shallow 5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c\n" +
+		"0000"
+
+	// Use the raw message as our input.
+	input := strings.NewReader(raw)
+
+	// Create a advref.Decoder reading from our input.
+	d := advrefs.NewDecoder(input)
+
+	// Decode the input into a newly allocated AdvRefs value.
+	ar := advrefs.New()
+	_ = d.Decode(ar) // error check ignored for brevity
+
+	// Do something interesting with the AdvRefs, e.g. print its contents.
+	fmt.Println("head =", ar.Head)
+	fmt.Println("capabilities =", ar.Capabilities.String())
+	fmt.Println("...")
+	fmt.Println("shallows =", ar.Shallows)
+	// Output: head = a6930aaee06755d1bdcfd943fbf614e4d92bb0c7
+	// capabilities = multi_ack ofs-delta symref=HEAD:/refs/heads/master
+	// ...
+	// shallows = [5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c]
+}
+
+func ExampleEncoder_Encode() {
+	// Create an AdvRefs with the contents you want...
+	ar := advrefs.New()
+
+	// ...add a hash for the HEAD...
+	head := core.NewHash("1111111111111111111111111111111111111111")
+	ar.Head = &head
+
+	// ...add some server capabilities...
+	ar.Capabilities.Add("symref", "HEAD:/refs/heads/master")
+	ar.Capabilities.Add("ofs-delta")
+	ar.Capabilities.Add("multi_ack")
+
+	// ...add a couple of references...
+	ar.References["refs/heads/master"] = core.NewHash("2222222222222222222222222222222222222222")
+	ar.References["refs/tags/v1"] = core.NewHash("3333333333333333333333333333333333333333")
+
+	// ...including a peeled ref...
+	ar.Peeled["refs/tags/v1"] = core.NewHash("4444444444444444444444444444444444444444")
+
+	// ...and finally add a shallow
+	ar.Shallows = append(ar.Shallows, core.NewHash("5555555555555555555555555555555555555555"))
+
+	// Encode the advrefs.Contents to a bytes.Buffer.
+	// You can encode into stdout too, but you will not be able
+	// see the '\x00' after "HEAD".
+	var buf bytes.Buffer
+	e := advrefs.NewEncoder(&buf)
+	_ = e.Encode(ar) // error checks ignored for brevity
+
+	// Print the contents of the buffer as a quoted string.
+	// Printing is as a non-quoted string will be prettier but you
+	// will miss the '\x00' after "HEAD".
+	fmt.Printf("%q", buf.String())
+	// Output:
+	// "00651111111111111111111111111111111111111111 HEAD\x00multi_ack ofs-delta symref=HEAD:/refs/heads/master\n003f2222222222222222222222222222222222222222 refs/heads/master\n003a3333333333333333333333333333333333333333 refs/tags/v1\n003d4444444444444444444444444444444444444444 refs/tags/v1^{}\n0035shallow 5555555555555555555555555555555555555555\n0000"
+}