Is there a way to reference the exact image location of an image built by a manifest elsewhere in the manifest?

[mb-krotos]

I have a basic service manifest where I build an image and define a "startup" sidecar. Here is the relevant section of the manifest:

image:
  build: 
    dockerfile: Dockerfile
    args:
      GIT_HASH: ${GIT_HASH}
  port: 8000
  depends_on:
    startup: success

sidecars:
  startup:
    essential: false
    command:
      [
        "some_bootstrap_command.sh",
      ]
    image: ${ECR_URI}:latest

This means that the startup image always points to the "latest" tag of the image built during that deployment. If something is wrong in that image (eg the bootstrap command fails), it means the rollback breaks because the 'startup' image for a previous version will also point to the "latest" tag, which will still fail.

Is there a way to set the image of the "startup" sidecar to the exact image built by the 'image' section?