Git and Github

What is Git?

Git is a Version Control System which helps us in tracking files, storing changes, retrieving files, performing rollbacks, maintaining history of the project and collaborating with other folks of the Open Source community. Git was written in C.

What is a Version Control System?

Version Control Systems also known as VCS also help us in tracking files, recovering files, figuring out who introduced the issue, when the issue was introduced, rollback to previous working state and collaborate with other people in the Open Source Community.

What is Github / Gitlab / BitBucket?

It is a hosting service which hosts our git repositories on the internet so that other people could make changes to the project source code in the form of Pull Requests and also point out new Issues in the code as well. Along with that, having public git repositories hosted on such sites helps in getting feedback from Customers and other members of the Open Source Community which lead to improvements over a period of time.

What are the different types of VCS? What is the history of VCS?

• Local Version Control System

  • Instead of manually keeping track of the changes , it is better if a program does that for us instead

  • A Local VCS consists of a database which is used to keep track of all the changes to the files and folders

  • Drawback : As all the changes are stored on a local system, there is a chance of data loss if the hardware get's damage

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• Centralized Version Control System

  • Instead of sending .zip files to collaborate on a project, we can maintain a common server which hosts a common repository which many people can access

  • People can pull the code , update the code and push the changes back to the server where the remote repository is located

  • As most people would have some version of the codebase, it would be some what recoverable if the server get's damaged, but we may not be able to recover the codebase as a whole

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• Distributed Version Control System

  • A Distributed VCS is a system of computers and servers which are connected together in way that if data in any of the nodes is lost, it could be recovered via the other nodes ie computers and servers

  • Each node in the network contain an update version of the repository and has the ability to collaborate

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What are the benefits of using Git?

Git helps in maintaining the history of the project and collaborating with other folks of the Open Source community. It leads to faster release cycles and maintains integrity of the source code.

What is a Git Repository?

A Git Repository is a location where all your files, folders and source code are stored. This location can be remotely hosted on platforms such as Github and can also be available in our local systems.

What is a Git Commit?

A Git Commit is a milestone in the repository where the desired changes for a particular feature or bug fix are saved into the history of the Git repository.

What is a Git Working Tree?

Files and folders that are added to the Git repository residing outside the .git folder are known as the Git working tree.

Difference Between Git and SVN(Subversion)?

What is the git push command used for?

The git push command is used to push our changes and commits to the remote repository.

What is the git pull command used for?

The git pull command is used to update the head of the branch with the latest changes made in the remote repository.

It could be equated as :

git pull = git fetch + git merge

What is the difference between git fetch and git pull?

What is a Merge Conflict?

When two or more people make changes or commits to the same lines of code in a small period of time, Git will get confused that which change do we want to take. That conflict is called a Merge Conflict.

How do we resolve Merge Conflicts?

When we try to merge the respective branches, git would warn us if there is a conflict in the changes being made. In order to make the corrections, we would have to manually modify the content in the Conflict Resolution Markers and then merge the changes.

What is the difference between git revert and git reset?

git reset <commit_hash> : It is used to unstage the changes which have already been committed .
git revert <commit_hash> : This command is used to create a new commit that undoes the changes made in the previous commit. Here, a new commit is added to the history of the project instead of modifying the existing history.

What is a Draft in Github?

Draft Pull Requests enable us to prevent merging until we are satisfied with the changes and select the "Ready For Review" option. This option can be used when we still want to make some changes to the Pull Request or it could be used to ensure that there are proper discussions regarding the Pull Request before it gets merged.

What is Tagging in Git?

Tagging refers to marking major milestones in the project.

What is Forking in Git?

Forking is the process of creating a copy of the remote repository we want to work on , in our Github account. We can make the desired changes in the forked copy and then create a Pull Request for those changes to be merged in the original repository.

What does git clone command used for?

The git clone command is used for creating a copy of the remote repository which is present on Github in our local system. We can make the desired changes to the repository locally and then push it to Github later when needed.

What is git clean command used for?

The git clean command is used to clean the working tree by recursively removing files that are not under version control, starting from the current directory. It ignores cleaning directories and files in the .gitignore file unless it is specified.

What is git cherry-pick command used for?

git cherry-pick enables us to pick up specific commits from a branch within a repository and apply it to another branch. The commit hashes should be given in order to acquire the correct and desired changes.

Important Git and Linux Commands

cd <directory_name> : To change from one directory to another. cd stands for "Change Directory".
ls <directory_name/directory_path> : This command lists all the files and folders in the directory specified.
ls -a <directory_name/directory_path>: To list all the hidden files as well.
ls -l <directory_name/directory_path>: To list the information in detail.
pwd : It is used to print the current working directory.
mkdir <directory_name> : To make a new directory in the current working directory.
touch <file_name>: To make a new file in the current working directory.
git init : This command initializes a git repository in our folder. It basically creates a .git file which tracks and stores all the history of the project.
rm -rf <file/directory/file_path/directory_path> : To delete or remove an unwanted file or directory.
git config : This command is used to configure the username and email address of the user.
git status : It shows what are the files that have been added , delete or updated. It shows the changes which are not currently saved in the git repository. It shows all the files in the staging area. If the files are not added, they are shown in "Red" colour , else they are shown in "Green" colour.
git add <directory_path/directory_name/file_name/file_path> : It is used to stage the desired changes in the staging area.
git commit <directory_path/directory_name/file_name/file_path> : This command is used to commit or store the changes made in the repository to the .git folder which was created when we initialized git. After writing this command , we would have to deal with the vim editor to write the "Title" and "Body" of the commit.
git commit -m"<message>" : Used to commit the changes directly with the message specified in the -m tag .
git commit -s : This command is used to make commit messages along with signing the DCO.
git commit --amend -s : If you have only one commit or the latest commit in the Pull Request is missing a sign-off, this command is the simplest way to fix it.
git restore --staged <directory_path/directory_name/file_name/file_path> : If you want to remove some changes from the stage, we use this command.
git log : It shows all the commit history of the project.
git reset <commit_hash_id> : It will move the data from the committing area to the unstaging area. Provide the previous hash value if you want to delete the next one.

NOTE : We cannot remove a particular commit from the middle. Each commit has a hash id and these commit messages are built on top of each other. We can unstage these commits by using the "git reset" command and then commit the desired changes from the changes which we just unstaged.

git stash : It is used when you want to work on a clean codebase and don't want to save your progress as a separate commit. It moves the changes in the staging area to the stash area.
git stash pop : This command is used to bring all the changes which were stashed back to the staging area.
git stash clear : This command is used to remove the changes which are in the stash area.
git remote add origin <url> : Command to attach a url to our local repository. "remote" here means that we are working with urls', origin is basically the name of the url which by convention points to the repositories in our account and the <url> is the url we are connecting our repository to. "upstream" url refers to the repository from which I created a fork.
git remote -v : To list down all the remote urls' which are connected.
git help : Gives a list of commands that we can use with git.
git push origin master : This command is used to push the commits and changes that we have made locally to the remote repository.
git branch : To list out all the branches present.

NOTE : Never commit on the main branch. A good practice is to create new branches for new features so that the users are not affected.

git checkout <branch_name> : To change the branch to <branch_name>. By default the name of the branch is "main". Previously it was known as "master".
git merge <branch_name> : This command is used to merge <branch_name> to the main or master branch.
git branch --merged : This command is used to list branches that have been merged into the current branch.
git branch --no-merged : This command is used to list branches that have not been merged into the current branch.
git push origin master -f : If we delete a commit or we want the remote repository to look exactly like our local repository without throwing any errors, we would have to force push the changes.
git reset <commit_hash> : It is used to unstage the changes which have already been committed .
git reset --hard <commit_hash>: It is used the reset the git repository to the commit with the provided hash value in hard mode which tells Git to overwrite all the changes in the working directory too.
git revert <commit_hash> : This command is used to create a new commit that undoes the changes made in the previous commit. Here, a new commit is added to the history of the project instead of modifying the existing history.
git diff : This command is used to view the changes made.
git clean -n : Shows all the untracked files which would be cleaned.
git clean --force : To clean all the untracked files.
git clean --force -x -d : To clean all the untracked files along with untracked directories and untracked files in the .gitignore file.
git commit --amend -s : If we have only one commit or the latest commit in the PR is missing a sign-off, the simplest way to fix this is to run this command.

How do I make sure that the main branch of the fork of the project is always updated with respect to the main branch of the upstream repository?

Method 1:

- Click the Sync Button in Github

Method 2:

- git checkout main              : Checkout to the main branch
- git fetch --all --prune        : Fetch all the branches, even the deleted ones
- git reset --hard upstream main : Resetting main branch of origin to main branch of upstream
- git push origin main           : Pushing the changes to our fork

Method 3:

- git pull upstream main         : Pull all the changes from upstream main branch
- git push origin main           : Push all the changes to origin main branch

How to squash commits into one single commit?

Method 1:

- git reset <commit_hash>
- git add .
- git commit

Method 2:

- git rebase -i <commit_hash>
- Replace "pick" with "s" where ever you deem necessary
- Write commit message
- git push origin main -f

Conclusion

In the dynamic world of software development, mastering Git and GitHub is essential for effective version control, seamless collaboration, and efficient project management. Git's robust features allow developers to track changes, manage branches, and maintain a detailed history of their code, while GitHub enhances these capabilities with cloud-based hosting, community engagement, and powerful tools for code review. Together, Git and GitHub streamline development processes, improve code quality, and foster a culture of collaboration and innovation, making them indispensable tools for developers at any level.

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