Upload Photo
Use GitHub CLI 2.99 or newer. Check and upgrade it if needed:
gh --version
brew upgrade gh
Attach a file to a new comment, putting alt text after #:
gh pr comment <n> --attach './shot.png#Alt text'
gh issue comment <n> --attach './shot.png#Alt text'
gh pr create, gh pr edit, gh issue create, and gh issue edit also accept repeatable --attach flags, with at most 50 files.
To place an image in the body, reference the same path:
printf '\n' | gh pr comment <n> --body-file - --attach './shot.png#Alt text'
GitHub rewrites that Markdown reference to the uploaded asset. Unreferenced attachments are appended to the comment.
There is no standalone “get a URL” command. The asset URL lives in the posted comment; read it back with gh api repos/{owner}/{repo}/issues/comments/<id> --jq .body.