How not to write an CI/CD build pipeline

If your build workflow/pipeline triggers on a push or merge to master and it needs push some changes back upstream, say for Github Pages or something, make sure it does so to a seperate branch or a submodule.

It seems obvious but I just wrote a workflow that did the complete opposite of that and got this Git error whenever I tried to push a change to the repo. The build was obviously completing its run, committing new changes to master before I could do a git pull, and push my local modifications. I must admit, I was rather confused for a moment before realising my mistake.

 ! [rejected]        master -> master (fetch first)
error: failed to push some refs to '[email protected]:spaghettiwews/trailers.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

I ended up with 200+ commits in the space of 45 minutes (after unknowingly kicking off my infinite loop, I had gone off to do other things, chuffed that the workflow was now working as expected).

Luckily, this was on the free Github Actions plan. Can you imagine doing something like this on a paid plan, on a Friday, not realising it and knocking off for the weekend. 😂

NB: To end the loop I had to edit the workflow file directly on Github, temporarily commenting out the part that pushing changes to the repo.