How do you check for differences? #1040

Bit of a n00b question so apologies in advance.

I am trying to write a little script that,

1. pull the repo
2. Check if that pull included any changes
3. If there have been changes, restart a target program

I have found several ways of checking for changes but none seem to work. Each time, I tested by making a change in my sandbox repo directly on GitHub and then executed the pull, so that the change is applied on my PC. For example,

changed_files = [item.a_path for item in repo.index.diff(None)]

Always appears to output an empty list. This seems to be what the tutorial suggests so I'm not sure why it does not work.

    current = repo.head.commit

    if current == repo.head.commit:
        print("Repo not changed. Sleep mode activated.")
        return 0
    else:
        print("Repo changed! Activated.")
        return 1

Always returns 0.

    diff = repo.git.diff(repo.head.commit.tree)
    print(diff)

When I checked the output when there was a change vs the output where there was no change, both outputs were the same.

What am I doing wrong here?

I have also found a SO question that was asked some time ago but never answered, so I'm not alone in this! Comments in that suggested git diff however I think I have tried that with the first method.

What is the best way to check if a pull has introduced changes since the last pull?