Add default branch to repository edit event (google#2995)

Fixes: google#2994.

Author: caseyduquettesc

github/event_types.go

@@ -388,11 +388,12 @@ type GollumEvent struct {
 // EditChange represents the changes when an issue, pull request, comment,
 // or repository has been edited.
 type EditChange struct {
-	Title *EditTitle `json:"title,omitempty"`
-	Body  *EditBody  `json:"body,omitempty"`
-	Base  *EditBase  `json:"base,omitempty"`
-	Repo  *EditRepo  `json:"repository,omitempty"`
-	Owner *EditOwner `json:"owner,omitempty"`
+	Title         *EditTitle         `json:"title,omitempty"`
+	Body          *EditBody          `json:"body,omitempty"`
+	Base          *EditBase          `json:"base,omitempty"`
+	Repo          *EditRepo          `json:"repository,omitempty"`
+	Owner         *EditOwner         `json:"owner,omitempty"`
+	DefaultBranch *EditDefaultBranch `json:"default_branch,omitempty"`
 }
 
 // EditTitle represents a pull-request title change.
@@ -442,6 +443,11 @@ type EditSHA struct {
 	From *string `json:"from,omitempty"`
 }
 
+// EditDefaultBranch represents a change of repository's default branch name.
+type EditDefaultBranch struct {
+	From *string `json:"from,omitempty"`
+}
+
 // ProjectChange represents the changes when a project has been edited.
 type ProjectChange struct {
 	Name *ProjectName `json:"name,omitempty"`