Merge pull request #1080 from buildpacks/dont-calculated-diffIDs-twice

Dont calculate buildpack layer diffIDs twice when creating a builder
Signed-off-by: David Freilich <[email protected]>

internal/builder/builder.go

@@ -306,17 +306,17 @@ func (b *Builder) Save(logger logging.Logger, creatorMetadata CreatorMetadata) e
 			return err
 		}
 
-		if err := b.image.AddLayer(bpLayerTar); err != nil {
+		diffID, err := dist.LayerDiffID(bpLayerTar)
+		if err != nil {
 			return errors.Wrapf(err,
-				"adding layer tar for buildpack %s",
+				"getting content hashes for buildpack %s",
 				style.Symbol(bp.Descriptor().Info.FullName()),
 			)
 		}
 
-		diffID, err := dist.LayerDiffID(bpLayerTar)
-		if err != nil {
+		if err := b.image.AddLayerWithDiffID(bpLayerTar, diffID.String()); err != nil {
 			return errors.Wrapf(err,
-				"getting content hashes for buildpack %s",
+				"adding layer tar for buildpack %s",
 				style.Symbol(bp.Descriptor().Info.FullName()),
 			)
 		}