01-08-common-errors.qmd

# Common errors

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE, fig.align = "center")
```

## Merge conflicts

* These can happen if e.g., 
  - you forget to pull down the latest changes from GitHub (I find it's easy to forget to do this in the morning)
  - if you're working on a project with multiple people
    - you both create new branches
    - they send in their PR first and it's merged
    - then you send in your PR which edits some of the same lines
* Let's say I made changes yesterday which I pushed to GitHub
  - The next day I restart work on a different computer, GitHub Desktop will show for example  
    ```{r}
    knitr::include_graphics("img/pulling-from-github.png")
    ```  
- But you forget to click "Pull origin"
- If you make commits onto a branch on which there are not yet pulled commits on GitHub you'll get a merge error when you eventually click "Pull origin"  
  ```{r}
  knitr::include_graphics("img/ghd-resolve-conflicts-before-merge.png")
  ```  
- You could resolve conflict e.g., in VSCode  
  ```{r}
  knitr::include_graphics("img/vscode-git-merge-resolve.png")
  ```  
- We can see this can happen when we see both up and down arrows in Pull origin box (but not always)  
  ```{r}
  knitr::include_graphics("img/ghd-potential-conflict.png")
  ```  
* Fix
  - Move your changes to a new branch  
    ```{r}
    knitr::include_graphics("img/ghd-create-branch-from-commit.png")
    ```  
  - Move back to `master`/`main` and revert/undo the changes there, then edit the files so they show no changes  
    ```{r}
    knitr::include_graphics("img/ghd-revert-changes-in-commit.png")
    ```  
    
    ```{r}
    knitr::include_graphics("img/ghd-undo-commit.png")
    ```  
  - Pull down the changes from GitHub to the relevant branch  
    ```{r}
    knitr::include_graphics("img/ghd-all-is-well.png")
    ```  
  - Merge changes from your new branch into the `main`/`master`/relevant branch
- See the GitHub documentation for more information about merge conflicts
  - [here](https://docs.github.com/en/github/collaborating-with-pull-requests/addressing-merge-conflicts/about-merge-conflicts)
  - Resolving a merge conflict [here](https://docs.github.com/en/github/collaborating-with-pull-requests/addressing-merge-conflicts/resolving-a-merge-conflict-on-github)

## No content changes found

- If you see the following message from Git that a file has changed but there are *No content changes found*  
  ```{r}
  knitr::include_graphics("img/no-content-changes-found.png")
  ```  

- This is most likely caused by working with colleagues using different operating systems, because they save text files with different line ending characters (`CRLF` on Windows, `LF` on macOS/Linux/Unix)

- You can usually simply right click on the offending file in GitHub Desktop and *Discard changes*  
  ```{r}
  knitr::include_graphics("img/no-content-changes-found-discard-changes.png")
  ```  
- Additionally you can set the following option at the top of your `.gitattributes` file
  ```  
  # Auto detect text files and perform LF normalization
  * text=auto
  ```