Fix invalid Docker image tag on PR builds

[Copilot]

The docker/metadata-action {{branch}} placeholder resolves to an empty string on pull_request events, producing the tag :-afc54f8 — an invalid Docker reference that fails the build.

Change

• .github/workflows/docker-publish.yml: Replace dynamic prefix={{branch}}- with the static prefix=sha-, producing a consistently valid tag (sha-<short-sha>) across both push and pull_request events.

-          type=sha,prefix={{branch}}-
+          type=sha,prefix=sha-

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add share button with URL-encoded markdown for easy sharing</issue_title>
<issue_description>## Feature Request: Share Button

Similar to how mermaid-js/mermaid-live-editor allows sharing of diagrams using URL encoding and compression (using pako), I propose implementing a share button for this Markdown viewer:

Expected Behavior

• Add a Share button in the viewer/editor toolbar.
• When clicked, the entire markdown content should be compressed (e.g., using pako or lz-string) and encoded as a URL-safe string.
• The encoded string should be embedded into the URL (preferably in the hash, e.g. #share=).
• User can share this URL and recipients will see the same markdown content when opening the link, decoded locally in the app.
• No cloud/server storage needed; data lives in the link itself.

Inspiration

• See how mermaid-live-editor uses pako for diagram sharing (repo link).
• This is effective for static sites, enabling state sharing without any backend.

Advantages

• Fully static – no server or cloud dependency
• Safe (data not sent to server)
• Enables easy collaborative sharing and reproducibility

Considerations

• Handle large documents gracefully (show error if content too large for URL)
• Use URL fragment instead of query string to avoid leaking content to servers
• Use clipboard copy fallback in browsers where sharing API is unavailable

Implementation Suggestion

• Use pako (for consistency with mermaid-live-editor) or optionally lz-string
• Add decode logic on app load to populate viewer if share fragment is present
• Add UI for sharing/copying link

</issue_description>

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

• Fixes Add share button with URL-encoded markdown for easy sharing #30

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
markdown-viwer	Ready	Preview, Comment	Mar 4, 2026 4:53am

[cloudflare-workers-and-pages]

Deploying markdown-viewer with    Cloudflare Pages

Latest commit:	92c2fdf
Status:	✅  Deploy successful!
Preview URL:	https://078d9bb9.markdown-viewer.pages.dev
Branch Preview URL:	https://copilot-add-share-button-mar.markdown-viewer.pages.dev

View logs

[cloudflare-workers-and-pages]

Deploying markdownviewer with    Cloudflare Pages

Latest commit:	92c2fdf
Status:	✅  Deploy successful!
Preview URL:	https://808e69ee.markdownviewer.pages.dev
Branch Preview URL:	https://copilot-add-share-button-mar.markdownviewer.pages.dev

View logs