[toaster0123]

Follow-up to #2.

The new snapshot workflow can publish two commits to the same daily snapshot concurrently, allowing an older commit to replace newer snapshot metadata. Release retries also allocate a new version after a tag has already been pushed, and missing publishing credentials are only detected after creating the release.

Changes

• Serialize snapshot uploads without cancelling an upload in progress, and skip commits that no longer match the head of master before uploading.
• Check all publishing credentials before creating a tag or GitHub release.
• Record the originating workflow run in an annotated release tag. Retries reuse that version and verify its commit, including when retried on another day. A new dispatch still allocates a new daily version.
• Reuse an existing GitHub release, and skip Maven uploads that a previous attempt recorded as successful. Abort if publishing history cannot be read.
• Propagate version-helper errors and document the retry/snapshot behavior.

Validation

• Existing scripts/next-version-test.sh: all 15 checks passed.
• YAML parsing and Bash syntax checks passed.
• Executed the actual workflow shell blocks against an isolated local Git remote, with GitHub and Maven calls mocked. Covered missing credentials, fresh-checkout retries on a later day, missing/existing releases, distinct dispatches of the same commit, mismatched/ambiguous tags, lightweight tags, failed/successful Maven attempts, unreadable history, stale snapshots, and helper/remote lookup failures.
• No release or Sonatype publication was triggered during validation.

The retry guard recognizes uploads recorded as successful by GitHub Actions. It does not claim transactional recovery when a remote upload is accepted but the client loses the response.

[jaime-jmebot]

This is a solid set of improvements to the snapshot and release workflows!

• Snapshot Concurrency: Serializing uploads and checking master HEAD prevents stale or concurrent commits from overwriting snapshot metadata.
• Release Retries & Tag Reuse: Checking credentials upfront and tagging releases with the workflow run marker enables reliable, idempotent retries.
• Publication Check: Reusing existing GitHub releases and skipping Sonatype uploads if a previous run attempt already succeeded prevents duplicate publish attempts.

Everything looks clean and well-tested. Great work!