fix(build): ensure imageSpec preserves CMD and ENTRYPOINT behavior for compatibility

If CMD is defined from the base image, setting ENTRYPOINT will reset CMD to an empty value. In this scenario, CMD must be defined in the current image to have a value.

https: //docs.docker.com/reference/dockerfile/#understand-how-cmd-and-entrypoint-interact
Signed-off-by: Aleksei Igrychev <aleksei.igrychev@palark.com>

Author: alexey-igrychev

pkg/build/stage/image_spec.go

@@ -54,6 +54,26 @@ func (s *ImageSpecStage) PrepareImage(ctx context.Context, _ Conveyor, _ contain
 			StopSignal: s.imageSpec.StopSignal,
 		}
 
+		// Entrypoint and Cmd handling.
+		{
+			// If CMD is defined from the base image, setting ENTRYPOINT will reset CMD to an empty value.
+			// In this scenario, CMD must be defined in the current image to have a value.
+			// rel https://docs.docker.com/reference/dockerfile/#understand-how-cmd-and-entrypoint-interact
+			if s.imageSpec.Entrypoint != nil {
+				newConfig.Entrypoint = s.imageSpec.Entrypoint
+				if s.imageSpec.Cmd == nil {
+					newConfig.ClearCmd = true
+				}
+			}
+
+			if s.imageSpec.Cmd != nil {
+				newConfig.Cmd = s.imageSpec.Cmd
+			}
+
+			newConfig.ClearCmd = newConfig.ClearCmd || s.imageSpec.ClearCmd
+			newConfig.ClearEntrypoint = newConfig.ClearEntrypoint || s.imageSpec.ClearEntrypoint
+		}
+
 		serviceLabels := s.stageImage.Image.GetBuildServiceLabels()
 		mergedLabels := util.MergeMaps(s.imageSpec.Labels, serviceLabels)
 		resultLabels, err := modifyLabels(ctx, mergedLabels, s.imageSpec.Labels, s.imageSpec.RemoveLabels, s.imageSpec.ClearWerfLabels)
@@ -86,19 +106,19 @@ func (s *ImageSpecStage) PrepareImage(ctx context.Context, _ Conveyor, _ contain
 		}
 
 		newConfig.ClearHistory = s.imageSpec.ClearHistory
-		newConfig.ClearCmd = s.imageSpec.ClearCmd
-		newConfig.ClearEntrypoint = s.imageSpec.ClearEntrypoint
 
 		stageImage.Image.SetImageSpecConfig(&newConfig)
 	}
 
 	return nil
 }
 
+const imageSpecStageCacheVersion = "2"
+
 func (s *ImageSpecStage) GetDependencies(_ context.Context, _ Conveyor, _ container_backend.ContainerBackend, _, _ *StageImage, _ container_backend.BuildContextArchiver) (string, error) {
 	var args []string
 
-	args = append(args, "1")
+	args = append(args, imageSpecStageCacheVersion)
 	args = append(args, s.imageSpec.Author)
 	args = append(args, fmt.Sprint(s.imageSpec.ClearHistory))