add custom tag for stages image, for build-kit only

[KawtharAlakri]

This PR supposed to fix the issue #157 and allow custom tag naming for the stages/cache image for build kit.

[whoan]

Hi @KawtharAlakri. Thank you for your pull request.
I am not sure it solves much as latest was used only for the last stage and your change only allows you to change the tag of the latest stage. If you have an image which has N stages, the previous ones will keep on having the default value:

docker-build-with-cache-action/docker-build.sh

Line 170 in 272668a

stage_image=$(_get_full_stages_image_name):$stage_number

Unless I am missing something, I think I am not going to merge this one.

[KawtharAlakri]

Hi @whoan
I updated the code to add the custom name to the stages as well as fixing the your comments.

[whoan]

@KawtharAlakri I have no time to test this now as I am moving but please bear with me I will get to it soon

[whoan]

this would make all stages to have tags like latest-1, latest-2, ... under legacy behavior (no buildkit) which I don't see it better than current behav.

[whoan]

@KawtharAlakri Could you please clearly state what problem this new attribute is fixing? I tried to put some reasoning about original decision in #157

I am still not sure this is really useful. I can still change latest to something else if that's bothering for the unique cache image when Buildkit is used, but would like to know why current behavior is a problem first.

[KawtharAlakri]

@whoan Thanks for clarifying your original decision reasoning. However, the issue I faced (and probably the one who created the issue) is that I wanted to use this action in a context where multiple images are being built and stored in the same repository, which requires different naming for their cache to not overlap. and that was the only issue that prevented me from using your action, so I thought it worths some contribution.

[whoan]

@whoan Thanks for clarifying your original decision reasoning. However, the issue I faced (and probably the one who created the issue) is that I wanted to use this action in a context where multiple images are being built and stored in the same repository, which requires different naming for their cache to not overlap. and that was the only issue that prevented me from using your action, so I thought it worths some contribution.

I understand better now. Thanks.
Can't you fix that issue by using a different stages_image_name per build? in that way each build will have a different cache and will not overlap.

Update: Maybe I can use the same image name's tag for the cache?