Stable re-tags the same source commit as the last beta, so the extracted tree
is byte-identical and `git commit` would abort on "nothing to commit" under
set -euo pipefail, leaving the stable tag uncreated. Use --allow-empty and add
a promote.test.sh case that promotes a second identical-tree tag into the same
pub repo to guard the regression.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
boban