How do you checkout an earlier commit?

[acgetchell]

git reset --hard && git pull origin master --no-rebase && git checkout e4ce66e works in Travis-CI:

https://github.com/acgetchell/CDT-plusplus/blob/develop/.travis.yml#L265

And AppVeyor:

https://github.com/acgetchell/CDT-plusplus/blob/develop/.appveyor.yml#L56

But various tries and reading the documentation don't work:

Using git fetch:

acgetchell/CDT-plusplus@4b6efdd

https://github.com/acgetchell/CDT-plusplus/runs/1933909111?check_suite_focus=true#step:3:171

Using actions/checkout@v2 and telling it to fetch everything:

acgetchell/CDT-plusplus@12719e3

https://github.com/acgetchell/CDT-plusplus/runs/1933963102?check_suite_focus=true#step:3:168

And telling actions/checkout@v2 to run git checkout <SHA>:

acgetchell/CDT-plusplus@5afcbf0

https://github.com/acgetchell/CDT-plusplus/runs/1934015574?check_suite_focus=true#step:3:4

How do you get the earlier versions?