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, 58 insertions, 0 deletions

diff --git a/formats/packp/advrefs/advrefs.go b/formats/packp/advrefs/advrefs.go
new file mode 100644
index 0000000..ab4bcf5
--- /dev/null
+++ b/formats/packp/advrefs/advrefs.go
@@ -0,0 +1,58 @@
+// Package advrefs implements encoding and decoding advertised-refs
+// messages from a git-upload-pack command.
+package advrefs
+
+import (
+	"gopkg.in/src-d/go-git.v4/core"
+	"gopkg.in/src-d/go-git.v4/formats/packp"
+)
+
+const (
+	hashSize = 40
+	head     = "HEAD"
+	noHead   = "capabilities^{}"
+)
+
+var (
+	sp         = []byte(" ")
+	null       = []byte("\x00")
+	eol        = []byte("\n")
+	peeled     = []byte("^{}")
+	shallow    = []byte("shallow ")
+	noHeadMark = []byte(" capabilities^{}\x00")
+)
+
+// AdvRefs values represent the information transmitted on an
+// advertised-refs message.  Values from this type are not zero-value
+// safe, use the New function instead.
+//
+// When using this messages over (smart) HTTP, you have to add a pktline
+// before the whole thing with the following payload:
+//
+// '# service=$servicename" LF
+//
+// Moreover, some (all) git HTTP smart servers will send a flush-pkt
+// just after the first pkt-line.
+//
+// To accomodate both situations, the Prefix field allow you to store
+// any data you want to send before the actual pktlines.  It will also
+// be filled up with whatever is found on the line.
+type AdvRefs struct {
+	Prefix       [][]byte // payloads of the prefix
+	Head         *core.Hash
+	Capabilities *packp.Capabilities
+	References   map[string]core.Hash
+	Peeled       map[string]core.Hash
+	Shallows     []core.Hash
+}
+
+// New returns a pointer to a new AdvRefs value, ready to be used.
+func New() *AdvRefs {
+	return &AdvRefs{
+		Prefix:       [][]byte{},
+		Capabilities: packp.NewCapabilities(),
+		References:   make(map[string]core.Hash),
+		Peeled:       make(map[string]core.Hash),
+		Shallows:     []core.Hash{},
+	}
+}