Add docker transport to push image before final failure

Signed-off-by: TomSweeneyRedHat <tsweeney@redhat.com>

Closes: #42
Approved by: rhatdan

libpod/util.go

@@ -4,9 +4,17 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 )
 
+// Runtime API constants
+const (
+	// DefaultTransport is a prefix that we apply to an image name
+	// to check docker hub first for the image
+	DefaultTransport = "docker://"
+)
+
 // WriteFile writes a provided string to a provided path
 func WriteFile(content string, path string) error {
 	baseDir := filepath.Dir(path)
@@ -42,3 +50,8 @@ func FuncTimer(funcName string) {
 	elapsed := time.Since(time.Now())
 	fmt.Printf("%s executed in %d ms\n", funcName, elapsed)
 }
+
+// hasTransport determines if the image string contains '://', returns bool
+func hasTransport(image string) bool {
+	return strings.Contains(image, "://")
+}