session-undo-merge.qmd

---
title: "Introduction to Git and GitHub"
subtitle: "Session - Undo last merge"
---

## The benefit of working in increments

Working in small chunks, committing and using pull requests means that there are more points to revert back to if things go wrong

In GitHub, find the pull request and at the bottom is a button `Revert` and this doesn't disappear over time

## Revert button

![](img/github-revert-pr.PNG){fig-alt="Screenshot of a day old GitHub Pull Request with the Revert button highlighted"}

## History of mistakes

-   Using `Revert` in GitHub (and other ways to undo work) creates a new commit

::: incremental
-   This means that your commit history is a record of all your work, even mistakes
-   It's absolutely ok and not something to be anxious about (when it's code)
-   But if you do commit information that is sensitive this needs to be removed this needs to be treated as an incident or breach
:::

## Removing sensitive data from a repository

It's a thing that every user of GitHub needs to consider and GitHub has [guidance](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/removing-sensitive-data-from-a-repository) but does refer to a [tool](https://rtyley.github.io/bfg-repo-cleaner/) that needs installing

> If this isn't available to you it is still possible to purge a file and its commit history but as there are many different scenarios... [TiddlyWiki](http://sukima.github.io/GitFixUm/).

is like a choose your own adventure.

::: notes
Acknowledge making a mistake is scary and not an adventure! There will be people to help though, through the NHS-R Community and people should definitely feel they can ask for help.
:::

## When in doubt - make it private

You can change the visibility of a repository through the `Settings` tab in GitHub

It's possible to move a public repository to private and back again any number of times

## End session

### Acknowledgements

CDU Data Science Team blog [When things go wrong in GitHub](https://cdu-data-science-team.github.io/team-blog/posts/2022-11-09-when-things-go-wrong-in-github/)