Use image hash instead of string to calculate caching hash

[darkdragon-001]

Actual behavior

• Cache is re-used even if the image in the FROM changed.
• Cache is not used if if the image in the FROM is having the same sha but a different name/tag

Expected behavior Cache should be based on content.

To Reproduce Create parent and child Dockerfiles, tag images accordingly and use cache.

Additional Information

• Dockerfile

  FROM scratch as parent
  RUN echo "parent" > /identifier

  ARG PARENT_TAG
  FROM parent:${PARENT_TAG} as child
  RUN cat /identifier

• Build Context: empty

• Kaniko Image: gcr.io/kaniko-project/executor:debug with sha256:3bc3f3a05f803cac29164ce12617a7be64931748c944f6c419565f500b65e8db

  Triage Notes for the Maintainers

  Description	Yes/No
  Please check if this a new feature you are proposing	- [ ]
  Please check if the build works in docker but not in kaniko	- [ ]
  Please check if this error is seen when you use --cache flag	- [x]
  Please check if your dockerfile is a multistage dockerfile	- [ ]

[gabyx]

This is indeed not a good solution as it is right now.

[git9am]

Experiencing exactly same issue. Is there any workaround for this "FROM based on ARG" scenario?