View the original community article here
Last tested: Nov 10, 2020
The commit Tag/SHA is accessible inside of Looker's commit history, as well as inside of the remote repo.
Inside of Looker's commit history, you can right click on a commit to copy the address - The SHA will be the last portion of the URL:
Inside of the remote repository, you can navigate to the commits page and copy the SHA from there (this example is GitHub):