How-to-release.md

How to release?

1. Please check whether CHANGELOG.md in root dir has unreleased contents.
2. Execute sh scripts/gen_release_markdown.sh {version} {milestone-number} commends to generate release markdown. And milestone-number cloud be found at the link, such as the milestone number of v1.0.28 is 2.
3. Please check whether the file named changes/{version}.md has all unreleased contents.
4. Please check whether the download link in changes/{version}.md working well. If having broken links, please upload the release files.
5. Commit & Push Github.
6. Press the release button in the GitHub console and paste the content of changes/{version}.md to here.