2 files changed, 24 insertions, 0 deletions
diff --git a/plumbing/format/packfile/parser.go b/plumbing/format/packfile/parser.go
index ee5c289..9ec838e 100644
--- a/plumbing/format/packfile/parser.go
+++ b/plumbing/format/packfile/parser.go
@@ -286,6 +286,7 @@ func (p *Parser) resolveDeltas() error {
 				if err := p.resolveObject(stdioutil.Discard, child, content); err != nil {
 					return err
 				}
+				p.resolveExternalRef(child)
 			}
 
 			// Remove the delta from the cache.
@@ -298,6 +299,16 @@ func (p *Parser) resolveDeltas() error {
 	return nil
 }
 
+func (p *Parser) resolveExternalRef(o *objectInfo) {
+	if ref, ok := p.oiByHash[o.SHA1]; ok && ref.ExternalRef {
+		p.oiByHash[o.SHA1] = o
+		o.Children = ref.Children
+		for _, c := range o.Children {
+			c.Parent = o
+		}
+	}
+}
+
 func (p *Parser) get(o *objectInfo, buf *bytes.Buffer) (err error) {
 	if !o.ExternalRef { // skip cache check for placeholder parents
 		b, ok := p.cache.Get(o.Offset)
diff --git a/plumbing/format/packfile/parser_test.go b/plumbing/format/packfile/parser_test.go
index b0b4af8..09f3f97 100644
--- a/plumbing/format/packfile/parser_test.go
+++ b/plumbing/format/packfile/parser_test.go
@@ -132,6 +132,19 @@ func (s *ParserSuite) TestThinPack(c *C) {
 
 }
 
+func (s *ParserSuite) TestResolveExternalRefsInThinPack(c *C) {
+	extRefsThinPack := fixtures.ByTag("codecommit").One()
+
+	scanner := packfile.NewScanner(extRefsThinPack.Packfile())
+
+	obs := new(testObserver)
+	parser, err := packfile.NewParser(scanner, obs)
+	c.Assert(err, IsNil)
+
+	_, err = parser.Parse()
+	c.Assert(err, IsNil)
+}
+
 type observerObject struct {
 	hash   string
 	otype  plumbing.ObjectType