FYI this repository is good. This yml may be helpful.

Requirements of CI build is described in the wiki page.
Besides, I have a plan of PR build to display documentation built from source files that PR merged.

Please help me with an assessment.

GitHub Action

Pros.

• Easily recognize types of event
• Many GitHub Actions already exist are available
• automatic GITHUB_TOKEN creation and expiration
• ?

Cons.

• It turns out that each step in a job is executed in a sort-of separate environment, and one step is unable to export environment variables that another step could read.
• ref. https://bravelab.io/blog/migrating-from-travisci-to-github-actions-1/
• An environment variable is hard to store an SSH key file.
• ?

Unknown.

• Can GitHub Action fully satisfy the requirements above?
• Is storing secrets easier than Travis ci?
• Can access across repositories easier?
• ?

The feature of automatic GITHUB_TOKEN creation is very helpful to push the results of PR builds. Moreover, the tokens have existence time limits, 60 minutes.

Two workflows, pr_build.yml and delete_pr_built_doc.yml, are now working!