plumbing: format/packfile, fix crash with cycle deltas

Resolving cycles relied on ObjectToPack objects having Original. This
is no longer true with the changes from #720. This commit changes:

* Save original type, hash and size in ObjectToPack
* Use SetObject to set both Original and resolved type, hash and size
* Restore original object before using BackToOriginal (cycle resolution)
* Update encoder test to check this case

Signed-off-by: Javi Fontan <jfontan@gmail.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/plumbing/format/packfile/object_pack.go b/plumbing/format/packfile/object_pack.go
index 1563517..284871f 100644
--- a/plumbing/format/packfile/object_pack.go
+++ b/plumbing/format/packfile/object_pack.go
@@ -23,6 +23,12 @@ type ObjectToPack struct {
 	// offset in pack when object has been already written, or 0 if it
 	// has not been written yet
 	Offset int64
+
+	// Information from the original object
+	resolvedOriginal bool
+	originalType     plumbing.ObjectType
+	originalSize     int64
+	originalHash     plumbing.Hash
 }
 
 // newObjectToPack creates a correct ObjectToPack based on a non-delta object
@@ -71,11 +77,24 @@ func (o *ObjectToPack) WantWrite() bool {
 	return o.Offset == 1
 }
 
+// SetOriginal sets both Original and saves size, type and hash
+func (o *ObjectToPack) SetOriginal(obj plumbing.EncodedObject) {
+	o.Original = obj
+	o.originalSize = obj.Size()
+	o.originalType = obj.Type()
+	o.originalHash = obj.Hash()
+	o.resolvedOriginal = true
+}
+
 func (o *ObjectToPack) Type() plumbing.ObjectType {
 	if o.Original != nil {
 		return o.Original.Type()
 	}
 
+	if o.resolvedOriginal {
+		return o.originalType
+	}
+
 	if o.Base != nil {
 		return o.Base.Type()
 	}
@@ -92,6 +111,10 @@ func (o *ObjectToPack) Hash() plumbing.Hash {
 		return o.Original.Hash()
 	}
 
+	if o.resolvedOriginal {
+		return o.originalHash
+	}
+
 	do, ok := o.Object.(plumbing.DeltaObject)
 	if ok {
 		return do.ActualHash()
@@ -105,6 +128,10 @@ func (o *ObjectToPack) Size() int64 {
 		return o.Original.Size()
 	}
 
+	if o.resolvedOriginal {
+		return o.originalSize
+	}
+
 	do, ok := o.Object.(plumbing.DeltaObject)
 	if ok {
 		return do.ActualSize()