git

Setup

• follow the instructions to create your own SSH-key pair to be used during the school: https://aspp.school/wiki/github-setup

Warm-Up

• how to start a repo from scratch?
  • git init local method
  • on GitHub git clone and either git push --force or git pull methods
• how to revert mistakes?
  • before commit:
    • git restore <file> [discard changes in the working directory] changes files
    • git restore --staged <file> [unstage changes ➔ opposite of git add <file>, does not modify the working directory]
  • after commit:
    • git revert <commit> [creates a new commit, modifies the working directory]
    • git reset <commit> [only reset the HEAD pointer, does not modify the working directory] rewrites history
    • git reset --hard <commit> [reset HEAD and modify working directory] rewrites history and changes files
• how to move the whole working directory to a specific point in history?
  • git checkout <commit> ➔ DETACHED HEAD problem, changes files
  • interaction with branches: git branch <branch_name> + git switch <branch_name>
• git gui: building commits along the way interactively (for the mess around type of workflows)

The Open Source model

• remotes: git pull <from_where> <what>, git push <where> <what>, git fetch <from_where> <what>, git merge <another_branch>
• GitHub: forks, branches and PRs: important ➔ explain fork vs. clone!!!
• strategies for keeping your fork up-to-date: your main and upstream's main, short-lived and long-lived topic branches
• a more thorough and detailed explanation can be found on the Numpy Contributor's Guide. This guide can be adapted to your own needs, see gitwash.
• make it clear that GitHub is just an option (git≠GitHub)

Scenarios

1. lone scientist working alone in the cellar without Internet (local git)
2. lone scientist uploading their software to the Internet in the hope it can be useful for other people (local git + one personal GitHub repo)
3. lone scientist sharing one software project with some other befriended lone scientist working in a different place (local git + o.p.G.r + permissions)
4. research group sharing software among members (local git + several GitHub repos + permissions + branches + [optional] PRs)
5. fully distributed software development using the most typical open source software workflows as used by numpy, scipy, sklearn, etc. (like above + we don't trust our contributors, i.e. work strictly with forks)