CORE-4786 make dev and main tags usable by flux

[monotek]

Type of Change

• Bugfix
• Enhancement / new feature
• Refactoring
• Documentation

Description

Add opt-in timestamp suffix to branch tags for Flux image automation

Why

Flux's image automation needs image tags it can order to pick the newest build. Our current branch tags (dev-36423e42, main-525f80d8) suffix the Git SHA, which isn't sortable — Flux can't tell which build is newer. Prod CalVer tags (2025.50.14) are already orderable via SemVer.

This adds an opt-in timestamp component to dev/main/master branch tags so they become sortable, while keeping the short SHA for traceability.

What

• New input docker-tag-timestamp (default false). When true, branch tags become <prefix>-<YYYYMMDDHHMMSS-UTC>-<short-sha>, e.g. dev-20260602143055-36423e42.
• Default is unchanged — existing consumers keep the legacy <prefix>-<short-sha> format. No breaking change.
• Prod (v*) tags and non-pushed feature-branch tags are untouched regardless of the flag.

Ref	Default	docker-tag-timestamp: 'true'
dev	dev-<sha>	dev-<timestamp>-<sha>
main/master	main-<sha>	main-<timestamp>-<sha>
v* (prod)	2025.50.14	(unchanged)

Flux usage

With the flag enabled, one ImagePolicy per environment:

# dev / stage — numerical sort on the extracted timestamp
filterTags:
  pattern: '^dev-(?P<ts>[0-9]+)-[0-9a-f]+$'
  extract: '$ts'
policy:
  numerical: { order: asc }
---
# prod — CalVer parses as SemVer
policy:
  semver: { range: '>=0.0.0' }

Checklist

• Write tests
• Make sure all tests pass
• Update documentation
• Review the Contributing Guideline and sign CLA
• Reference relevant issue(s) and close them after merging

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[monotek]

I have read the CLA Document and I hereby sign the CLA

[Copilot]

Pull request overview

Adds an opt-in timestamp component to dev/main/master branch image tags so Flux image automation can sort tags and select the newest build, while preserving the legacy <prefix>-<short-sha> format by default.

Changes:

• Introduces a new docker-tag-timestamp action input (default false) to generate sortable branch tags: <prefix>-<utc-timestamp>-<short-sha>.
• Refactors tag generation logic in scripts/generate-tags.sh via a branch_tag helper.
• Extends Bats tests and documents the new tag format and Flux policy guidance in the README.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
scripts/generate-tags.sh	Adds branch_tag helper to optionally insert a UTC timestamp into branch tags.
action.yml	Adds docker-tag-timestamp input and wires it to INPUT_DOCKER_TAG_TIMESTAMP env var.
tests/generate-tags.bats	Adds deterministic tests for timestamped branch tags and ensures prod tags remain unchanged.
README.md	Documents the new input and provides guidance for Flux image automation policies.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.