Merge branch 'js/default-branch-name-adjust-t5515'

Prepare a test script to transition of the default branch name to 'main'. * js/default-branch-name-adjust-t5515: t5515: use `main` as the name of the main branch for testing (conclusion) t5515: use `main` as the name of the main branch for testing (part 3) t5515: use `main` as the name of the main branch for testing (part 2) t5515: use `main` as the name of the main branch for testing (part 1)