<style> @font-face { font-family: Inter; src: url("/fonts/Inter/Inter-Bold.woff2") format("woff2"), url("/fonts/Inter/Inter-Bold.woff") format("woff"); } .reveal h1, .reveal h2 { font-family: "Inter"; font-optical-sizing: auto; font-weight: normal; font-style: normal; } .mermaid svg { width: 100%; height: 30%; } </style> # Introduction to Git <!-- Put the link to this slide here so people can follow -->  https://hackmd.io/@f-fra/rJwURt9y1g  &nbsp;&nbsp;&nbsp;&nbsp;  - Join the [GitLab team](https://teams.microsoft.com/l/team/19%3AiBEHvWyPK7Hq543OelkXb4jttoeo-x2bjUoexVEApAw1%40thread.tacv2/conversations?groupId=b0f6b139-5886-4175-a000-6ea1e7c8fef7&tenantId=5a9809cf-0bcb-413a-838a-09ecc40cc9e8)! --- ## The problem(s)... - "Where did I save that script again..?" - "Which version of that are you using?" - "Did you end up solving that bug we found the other day?" - "Good that you fixed that, can you send me the updated version?" - "I added this feature, can you integrate it in the code?" - "I SWEAR IT WAS WORKING YESTERDAY, I DON'T KNOW WHAT CHANGED" --- ## Manual backups can help, but... <img src="https://phdcomics.com/comics/archive/phd101212s.gif" height=700/> <!-- Amazing!! --> <small> Source: https://phdcomics.com/comics/archive.php?comicid=1531 ©️ Jorge Cham </small> --- ## ... the real&trade; solution - Version control systems (VCS)! - Keep everything you need in a single "bucket" (*repository*) - Make sure everyone has access to the latest developments - Keep track of the history of a document/software - Sustainable collaborative workflows - Different flavours: - Centralised: Concurrent versions system (CVS), Subversion (SVN), Perforce, ... - Distributed: Git, Mercurial, Bazaar, ... --- ## Keep track of the history of the code <img src="https://upload.wikimedia.org/wikipedia/commons/c/cb/Tig_v2.5.1_history_and_one_commit_details.png" /> --- ## Centralised vs distributed VCSs - Centralised: - One main remote repo that stores every version of the code - Client-server architecture - Every developer has only a local snapshot of the latest version - Pros: work really well with binary files, easier to learn - Cons: single point of failure, client-server communication can slow down development, only one person can work on a piece of code at a time --- ## Centralised vs distributed VCSs - Distributed: - Every peer has the whole history tree cloned on their device - Possible to work offline, servers only stores the difference between versions - Possibility to implement strong workflows and code-checking procedures - Pros: More resilient (everyone has a backup), flexible branching (tested locally), quick development cycles - Cons: steeper learning curve, suboptimal for large binary files --- ## Git structure and workflow <!--  --> ```mermaid %%{init: {'theme': 'default', 'gitGraph': {'rotateCommitLabel': true, 'useMaxWidth': false, 'showCommitLabel': false, 'nodeLabel': {'width':100, 'height': 30, 'x': 0, 'y': -10} }, }}%% --- title: Lesson development --- gitGraph commit commit branch julia_notebook checkout julia_notebook commit commit commit type: REVERSE commit checkout main branch python_notebook checkout python_notebook commit checkout main commit checkout python_notebook commit checkout main merge python_notebook commit commit ``` - The history of a repo is a directed acyclic graph (DAG) - Each arrow is a *branch* - Branches can be used as sandboxes to modify/develop things without affecting the main version - Each dot is a *commit*, i.e. a saved snapshot of your repo - Each commit should include a message (e.g. "fixed this bug") - Branches can then be *merged* back into the main path (blue) --- ## Git structure and workflow - Collaboration - <font color='#f00'>Remember</font>: Git is decentralised! - Every change you make is <font color='#f00'>local</font>! - This means that changes have to be *pushed* to the remote repo (e.g. GitHub) - It also means that the latest changes have to be *pulled* - Very easy to keep up with people's work: you just *pull* from the remote origin :) - During merges/pulls, code reviews and discussion, as well as tests, can be performed --- ## Logging in Git  --- ## Project management features - Couple of platforms based on git: GitHub, GitLab - Both have features such as: - access levels: for creating groups of maintainers / developers / reviewers + their code projects - planning: organize issues, pull-requests, milestones in a Kanban board - CI/CD: automatise workflows, deploy - RISE runs their own GitLab! - Join the [GitLab team](https://teams.microsoft.com/l/team/19%3AiBEHvWyPK7Hq543OelkXb4jttoeo-x2bjUoexVEApAw1%40thread.tacv2/conversations?groupId=b0f6b139-5886-4175-a000-6ea1e7c8fef7&tenantId=5a9809cf-0bcb-413a-838a-09ecc40cc9e8) - After 15 minutes, login to https://git.ri.se --- ## Let's give a look to the RISE Gitlab!