Entendendo GIT | (não é um tutorial!)

Retrospective and Introduction

In this section, Fabio Akita introduces himself and his new equipment setup. He also mentions that he will not be doing a retrospective since it is already February.

Introduction to Git

• Fabio talks about how he has been postponing talking about Git for a year now.

• He mentions that learning the basic commands of Git is simple, but he wants to provide insights that people may not know even if they have been using Git for a long time.

• Fabio talks about how before Git, many companies did not use any version control or used commercial products like Microsoft SourceSafe or Rational ClearCase.

The Birth of Git

• Fabio talks about listening to an interview with Junio Hamano on FLOSS Weekly in 2007 where Hamano explained what Git was.

• He explains that at the time, most companies were still using CVS or moving towards Subversion as their version control system.

• Fabio stumbled upon a tech talk by Linus Torvalds from May 2007 where Torvalds talked about the issues with previous version control systems and how BitKeeper was being used for the Linux kernel project.

The Need for Git

• Before the creation of Git, the Linux kernel project was maintained through patches and tarballs. When BitKeeper became unavailable, there were no good alternatives until Torvalds decided to create his own version control system.

Conclusion

In this section, Fabio concludes his discussion on Git and its history.

• Fabio concludes by stating that Git has become the most popular version control system in use today.

Problemas com versionamento de código

Nesta seção, o palestrante discute os problemas que surgem quando programadores não utilizam ferramentas de versionamento de código.

Problemas comuns sem ferramentas de versionamento

• Programadores iniciantes frequentemente cometem erros ao salvar seus arquivos e acabam perdendo versões anteriores.

• Duplicar arquivos antes de editar é ineficiente e pode levar a uma grande quantidade de arquivos desnecessários no diretório.

• Quando vários desenvolvedores trabalham em um mesmo projeto, podem ocorrer conflitos ao editar o mesmo arquivo. Ferramentas como SourceSafe ou ClearCase foram criadas para lidar com esse problema, mas ainda são limitadas.

• O uso do versionamento é essencial para evitar perda acidental de trabalho e gerenciar diferentes versões do código.

A ferramenta Diff

• A ferramenta Diff foi criada nos anos 70 para comparar diferenças entre dois arquivos. É importante estudar algoritmos e estruturas de dados para entender como ela funciona.

• Utilizando a subsequência comum mais longa entre dois strings, é possível marcar as diferenças entre os arquivos como "mais" ou "menos".

• Adicionando metadados sobre a localização da subsequência no arquivo original, é possível gerar um patch que pode ser utilizado pela ferramenta Diff.

Conclusão

• O uso do versionamento é essencial para gerenciar diferentes versões do código e evitar perda acidental de trabalho. A ferramenta Diff é uma das principais ferramentas utilizadas para comparar diferenças entre arquivos e gerar patches.

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Version Control Systems

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The Basics of Version Control Systems

• Version control systems were first introduced in the 80s and 90s. They allowed developers to configure a server where they could store their project, and each developer would install a client on their machine to connect to that server.

• The server was responsible for authenticating login credentials and granting access permissions to code. Developers could then download the code by checking it out, make modifications, and upload changes by checking it in.

• Branches were later introduced as a way for developers to work on separate features or bug fixes without interfering with the main project directory. However, managing branches became complicated when working with larger teams.

• GitHub's Pull Requests feature is essentially a branch of the project that simplifies collaboration.

The Evolution of Version Control Systems

• Subversion was created as an improvement over CVS but still had issues with managing branches until version 1.5 was released in 2008.

• BitKeeper revolutionized version control systems by making operations like branching and merging much simpler and faster than before.

• Linus Torvalds migrated development of the Linux kernel to BitKeeper until restrictions were placed on its use. This led to the creation of Git in 2005, which solved many performance issues present in other version control systems.

The transcript is primarily focused on discussing the history and evolution of version control systems, including their basic functionalities and common issues faced by developers. It also highlights how newer technologies like GitHub's Pull Requests feature have simplified collaboration among developers.

Git and Version Control

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Git vs. Subversion/CVS

• Git automatically merges conflicts, while older systems like Subversion or CVS require manual conflict resolution.

• Working in branches and merging frequently is common practice in Git, but was avoided in older systems due to the cost of creating branches and complicated merges.

• In older systems, developers often worked on the same version/trunk to avoid conflicts, leading to debates over who had commit access.

Basic Git Terminology

• git clone pulls a copy of a project onto your machine.

• git add marks changes made to files, while git commit packages those changes into a patch since the last commit.

• Commits are hashed using SHA-1 for reliability and integrity purposes.

Personal Anecdotes

• The speaker shares their experience with CVS and Subversion creating directories that caused issues with Visual Studio projects on Windows machines. They created a patch for TortoiseSVN to create subdirectories with underscores instead of periods to solve this issue.

Git Internals

Nessa seção, o palestrante explica como funciona o repositório do Git e como ele armazena os arquivos.

Repositório do Git

• O repositório do Git é um banco de dados de objetos.

• Os objetos são blobs que contêm conteúdo e trees que contêm metadados.

• O diretório .git/objects armazena esses objetos em subdiretórios com nomes que parecem hashes SHA-1.

• É possível recuperar qualquer arquivo apagado usando o comando git checkout.

Metadados

• Para organizar os blobs, precisamos criar metadados que também são objetos, mas em vez de tipo blob eles são tipo tree ou árvore.

• Os metadados incluem informações como nome do arquivo, estrutura de diretórios e atributos.

• Para adicionar metadados a um arquivo, usamos o comando git update-index para estacionar as modificações na área intermediária (stage).

• Em seguida, usamos o comando git write-tree para gerar um objeto de tree com esses metadados.

Commits

• Um commit é um objeto que aponta para uma árvore (tree) e contém informações sobre quem fez a alteração e quando foi feita.

• Para criar um commit, usamos o comando git commit -m "mensagem" após configurar nosso nome e email no Git.

I apologize, but I cannot provide a summary of the transcript without having access to it. Please provide me with the transcript so that I can create a comprehensive and informative markdown file for you.

Git Branching and Merging

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Advantages of Git over CVS and Subversion

• Git has the advantage of marking the commit of origin for each branch, which allows it to determine which commit started a branch. This information is not available in CVS or Subversion before version 1.5.

• When merging branches, Git can look back at the original version of a file to determine which changes were made by each contributor. This allows it to automatically resolve conflicts that would be difficult or impossible to resolve in CVS or Subversion.

Difference between Rebase and Merge

• The rule for using rebase is to never use it on a branch that mirrors an official repository branch (e.g., master). Instead, rebase should be used on new feature or experimental branches created on your local machine.

• Rebase involves rewinding your branch back to its starting point, applying any new commits from the original branch, and then applying your own commits on top. Merge creates a new commit that links two branches together.

Example Scenario

• Alice and Bob are two developers working on separate copies of a project. They need to merge their work together but have conflicting changes on the same line of code.

• In CVS or Subversion, this conflict would require manual intervention from both developers. In Git, however, the system can automatically determine which change was made first by looking at the original version of the file.

• After resolving conflicts, Git creates a merge commit that links the two branches together. This allows each developer to continue working on their own branch and merge changes in the future without repeating the same conflicts.

The transcript contains additional information that may be useful for understanding Git branching and merging, but these are the most important points to take away from it.

Git and Subversion

In this section, the speaker talks about his experience with using both Git and Subversion. He explains how creating branches was not the issue, but merging them was a problem that Subversion took 8 years to fix. He also discusses how he was able to use Git even when working on projects that still used Subversion.

The Problem with Subversion

• The speaker had experience using both Git and Subversion.

• Creating branches in Subversion was marketed as simple, but merging them was difficult.

• It took 8 years for Subversion to fix the merge tracking issue.

• The speaker started using Git because of these issues.

Using Git with Subversion

• The speaker used an adapter to convert a repository from Subversion to Git.

• With this adapter, the speaker could work on a project in Git even if the client did not want to switch from Subversion.

• This is possible because of the distributed nature of systems like Git.

Cloning Repositories in Git

In this section, the speaker talks about cloning repositories in Git. He explains how it is possible to clone a repository locally or over a network, and how remote configurations can be changed easily.

Cloning Repositories Locally or Over a Network

• It is possible to clone a repository locally by copying it onto a USB drive or by connecting to the computer via SSH.

• When cloning a repository from GitHub, the only difference between it and a locally created repository is a few lines in the config file pointing to an internet address.

• Git does not require a central server to control everything.

Using Git on Windows

• The speaker talks about how Git was originally designed for use in a Linux terminal, but now it is easy to use on Windows with programs like Visual Studio Code and the Windows Subsystem for Linux (WSL).

Conclusion

In this section, the speaker concludes his talk by discussing how he forced his previous employer to switch from Microsoft SourceSafe to Git. He also talks about how he prefers using private installations of GitLab instead of public repositories like GitHub.

Switching from Microsoft SourceSafe to Git

• The speaker convinced his previous employer to switch from Microsoft SourceSafe to Git.

• He prefers using private installations of GitLab instead of public repositories like GitHub because he does not want third parties accessing his code or that of his clients.

A Brief History of Git

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The Early Days of Version Control Systems

• Developers migrated to GitLab due to its better features compared to Git.

• Corporations used centralized version control systems and limited access to code. This created unnecessary politics and made it easy for bad code to survive.

• The speaker introduced the concept of open-source code where all employees have access to all code, creating a more collaborative environment.

Why Git is Different

• Open-source code ensures that bad code does not survive longer than necessary and reduces politics in the workplace.

• The goal of this video is not a tutorial but rather an overview of why Git exists, what makes it different from other version control systems, and why it succeeded where others failed.

• GitHub's success led to widespread adoption of Git among developers.

Personal Experience with Git

• The speaker brought Chris Wanstrath and Scott Chacon, founders of GitHub, as speakers at conferences he organized.

• Using Git improved the speaker's life as a developer substantially since 2007.

Overall, this video provides a brief history of version control systems and explains why open-source code is important. It also highlights how Git differs from other version control systems and why it has become so popular among developers.