packfile: delta selection logic (#182)

* packfile: delta selection logic

- Implemented logic to assign deltas to objects

* Requested changes

* Improved tests and fix errors

1 files changed, 36 insertions, 0 deletions

diff --git a/plumbing/format/packfile/common_test.go b/plumbing/format/packfile/common_test.go
new file mode 100644
index 0000000..387c0d1
--- /dev/null
+++ b/plumbing/format/packfile/common_test.go
@@ -0,0 +1,36 @@
+package packfile
+
+import (
+	"testing"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+func newObject(t plumbing.ObjectType, cont []byte) plumbing.EncodedObject {
+	o := plumbing.MemoryObject{}
+	o.SetType(t)
+	o.SetSize(int64(len(cont)))
+	o.Write(cont)
+
+	return &o
+}
+
+type piece struct {
+	val   string
+	times int
+}
+
+func genBytes(elements []piece) []byte {
+	var result []byte
+	for _, e := range elements {
+		for i := 0; i < e.times; i++ {
+			result = append(result, e.val...)
+		}
+	}
+
+	return result
+}