upload-github-attachment

# Upload GitHub Attachment Use the bundled script so authentication, repository resolution, MIME detection, and URL extraction remain consistent. ## Requirements - Require the `gh` CLI and `curl`. - Prefer an existing `gh auth login` session. - When interactive `gh` authentication is unavailable, require `GH_TOKEN` or `GITHUB_TOKEN` in the environment. - Stop and ask the user to configure one of those authentication methods if `gh auth token` cannot resolve a token. Never print, persist, or interpolate the token into diagnostic output. ## Upload `<skill-dir>` is the directory that contains this `SKILL.md`. Run from a checkout of the destination repository: ```bash <skill-dir>/scripts/upload-github-attachment.sh /absolute/path/to/image.png ``` Specify the repository when the current directory cannot resolve it: ```bash <skill-dir>/scripts/upload-github-attachment.sh \ --repo OWNER/REPO \ /absolute/path/to/image.png ``` The script prints only the final `https://github.com/user-attachments/assets/...` URL. Embed it with `` for an image or `[label](URL)` for another file. ## Verification 1. Require a successful upload command and a returned `https://github.com/user-attachments/assets/...` URL. 2. Use that URL for the intended local file. Do not issue GET or HEAD requests to verify the uploaded asset. 3. Do not treat anonymous access returning 404 as an upload failure or a reason to stop the workflow. 4. After creating or editing GitHub content, reopen it and verify the attachment Markdown uses the returned URL. The upload endpoint is currently undocumented by GitHub. Treat a rejected upload request as a blocking capability change instead of committing PR-only artifacts. Background and the observed Bearer-token flow: <https://island94.org/2026/08/programmatically-upload-attachments-to-github-issues-pull-requests-comments>.