Set the default branch inside the event data (#354)

* set ${{github.event.repository.default_branch}}

* change `ok == false` to `!ok`

Co-authored-by: Casey Lee <cplee@nektos.com>

cmd/input.go

@@ -20,6 +20,7 @@ type Input struct {
 	noOutput        bool
 	envfile         string
 	secretfile      string
+	defaultBranch   string
 	privileged      bool
 }