Add workflow to upload minimal Alpine container to GHCR

[Copilot]

• Investigate CI failure
• Fix Docker tag format to handle PR builds correctly
• Test the fix by verifying workflow syntax
• Report completion

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add a workflow to upload some very small container package</issue_title>
<issue_description>could be some alpine or other tiny image, with at least some extra layer on top -- may be just create some timestamp.txt file inside the container with a time stamp when it was built.
Workflow should have dispatch capability but otherwise trigger only when file is changed and uploaded to packages when built on master branch (not on PRs)</issue_description>

<agent_instructions>see con/tinuous#222 for what it will be used</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Add a workflow to upload some very small container package #9

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[yarikoptic]

@copilot make it also build on PRs if Dockerfile changed, but not upload. This way we could test/ensure that it builds fine

[Copilot]

@copilot make it also build on PRs if Dockerfile changed, but not upload. This way we could test/ensure that it builds fine

Done in commit 98474fa. The workflow now:

• Builds on PRs when Dockerfile changes (without pushing to registry)
• Only logs in and pushes to GHCR on master branch
• Uses conditional push: ${{ github.ref == 'refs/heads/master' }} in the build step

[yarikoptic]

@copilot see and address fails to CI run on this PR

[Copilot]

@copilot see and address fails to CI run on this PR

Fixed in commit 1d02b34. The issue was that the Docker metadata action was generating an invalid tag format (-18dac0c) for PR builds because the {{branch}} placeholder was empty.

Changes:

• Added type=ref,event=pr to generate valid PR tags (e.g., pr-10)
• Restricted type=sha,prefix={{branch}}- to only run on the default branch
• Added type=sha without prefix for PR builds to generate valid short SHA tags

The workflow will now build successfully on PRs without pushing to the registry.