Reference – Version Control with Git

Key Points

What is Version Control	Version control is like an unlimited ‘undo’. Version control also allows many people to work in parallel.
Setting Up Git	Use `git config` with the `--global` option to configure a user name, email address, editor, and other preferences once per machine.
Creating a Repository	`git init` initializes a repository. Git stores all of its repository data in the `.git` directory.
Tracking Changes	`git status` shows the status of a repository. Files can be stored in a project’s working directory (which users see), the staging area (where the next commit is being built up) and the local repository (where commits are permanently recorded). `git add` puts files in the staging area. `git commit` saves the staged content as a new commit in the local repository. Write commit messages that accurately describe your changes. `git log` lists the commits made to the local repository.
Exploring History	`git diff` displays differences between commits. `git checkout` recovers old versions of files.
Collaborating	`git remote add origin` links a local repository to a remote one and names it ‘origin’. `git push` copies changes from a local repository to a remote repository. `git pull` copies changes from a remote repository to a local repository. Branches are versions of a repository that can contain different commits. Pull requests on GitHub can be used to merge different branches together. `git clone` copies a remote repository to create a local repository with a remote called origin automatically set up.
Conflicts	Conflicts occur when different commits change the same lines of the same file. The version control system does not allow changes to overwrite each other, but highlights conflicts so that they can be resolved. `git checkout -b` creates a new branch and checks it out at the same time. `git push -u` links a local branch with an ‘upstream’ branch on a remote repository. `git pull` can pull changes from one branch into another locally.
Ignoring Things	The `.gitignore` file tells Git what files to ignore.

Cheat Sheet

Many Git cheat sheets exist- here’s one example.

Glossary

Repositories

Repository: A directory set up to be able to track changes to specified files within it.
Tracked files: Files set up to have their changes tracked via Git.
Staging Area: A temporary record of the current state of all the tracked files, that can be turned into a commit.

Commits

Commit: A specific version of all the tracked files within a repository, that tracks the change made to them since the last commit.
Commit ID: A long string of letters that references a specific commit (e.g. 7716d1bb10d82548cf8000abde123d812494b707). Can use the first 7 as shorthand (e.g. 7bada3c).
HEAD: The most recent commit on the current branch.
HEAD~1: The commit 1 before the current HEAD. Can also be expressed as HEAD@{1}.

Branches

Branch: A version of the state of a repository. Commits to a repository are specific to a branch, so different branches can hold different versions of the same files. Branches start from a specific commit on an existing branch.
Master/main branch: The conventional name for the ‘base’ branch, and one that should be used for stable, reliable versions of the code.
Development/dev branch: A branch that comes off of the master branch, and is used for work-in-progress versions of the code. It is merged back into the master when you have a stable version.
Feature branch: A branch that comes off of the development branch, and is used to fix a bug or add a feature before being merged back into the development branch.

Remotes & merges

Remote repository: An online copy of the repository, that you can synchronise with and share. Conventionally called origin.
Upstream: For a branch, the default remote branch to push and pull to. Set using git push -u remote_name branch_name_on_that_remote.
Push: To send commits from the current branch to another branch, either locally or remote. Normally only used to push to the same branch on a remote repository.
Pull: To bring the commits from another branch, either local or remote, into the current branch. Can be used to synchronise your current branch with changes on a remote repository, or merge two branches together.
Pull request: On GitHub, a way of requesting that one branch pulls the commits from another into it. A way to merge branches.
Merge: Adding the changes from one branches’ commits to another branch. Should be done using pull or preferably via a pull request.
Merge conflict: When two different commits change the same lines of the same file. Occurs when trying to add commits from one branch to another branch using pull or push.
Conflict marker: A sequence of <<<<, ==== and >>>> added to a file to show where the merge conflict occurred. The section from <<<< to ==== is the version of the file in the current branch, the section from ==== to >>>> is the version of the file in the branch you’re trying to merge in.

Version Control with Git: Reference

Key Points

Cheat Sheet

Glossary

Repositories

Commits

Branches

Remotes & merges