the runner of "actions/checkout@v2" action is too old to run on GitHub Actions. update the action's version to fix this issue

shellcheck reported issue in this script: SC2086:info:1:10: Double quote to prevent globbing and word splitting

shellcheck reported issue in this script: SC2086:info:2:7: Double quote to prevent globbing and word splitting

shellcheck reported issue in this script: SC2086:info:3:12: Double quote to prevent globbing and word splitting

shellcheck reported issue in this script: SC2059:info:4:11: Don't use variables in the printf format string. Use printf '..%s..' "$foo"

shellcheck reported issue in this script: SC2086:info:4:58: Double quote to prevent globbing and word splitting

shellcheck reported issue in this script: SC2035:info:5:11: Use ./*glob* or -- *glob* so names with dashes won't become options

shellcheck reported issue in this script: SC2086:info:6:62: Double quote to prevent globbing and word splitting

shellcheck reported issue in this script: SC2035:info:6:71: Use ./*glob* or -- *glob* so names with dashes won't become options