General Terms

  • Repository (repo): a local repository tracks all the changes you made in that directory. In tangible form, it is a .git/ folder that lives inside the directory.

  • Branch: independent line of development typically used to develop new features without disturbing the rest of the repository. The default branch is called the “Master” branch.

  • Clone: the concept of a “clone” just means to copy the entire repository.

  • Conflict: when the same portion of a file is edited, it creates a conflict that has to be manually resolved before it can be merged together. This often is the reason why you cannot push a commit.

  • Commits: a “commit” adds your latest changes to your repository. If a change is not committed, Git would not recognize the change.

  • Fork: within the context of GitHub, to fork is to copy someone’s GitHub repository and put it in your GitHub account. Under the hood, it is just cloning their repository.

  • HEAD: refers to the latest commit in the branch you are at. By default, you are the most recent commit of the master branch. When you git checkout different_branch, HEAD is now at the most recent commit of different_branch. If you are not at the most recent commit of a branch (e.g., you git checkout a previous commit), you are now in a detached HEAD.

    • Note that changes made in a detached HEAD situation would not be recorded once you git checkout back to the HEAD of the branch or to a different branch.

Git Commands

  • git add: tells git which file’s changes you want to document. Formally, this is called adding a file to the “index/staging area”.

  • git branch: handles the creation, renaming and deletion of branches. Note that git checkout is used to switch between branches.

  • git checkout: revert (i.e., checkout) a file to a previous state. You can also checkout your entire folder, but it is potentially a dangerous move (puts you in a detached HEAD).

  • git clone: copies (download) a remote repo onto your local computer.

  • git commit: tells git to document the changes you specified using git add (i.e., the files in the staging area), with an accompanying commit message that you have to provide to explain what changes were made.

  • git diff: shows the difference between current state of a file/repository with a commit.

  • git fetch: fetches the changes that is in your remote repository GitHub. This command download the changes into the .git/ folder so you can compare changes to your local files, but it does not actually modify your files (i.e., files outside of the .git/ folder).

  • git init: creates a repository (the .git/ folder).

  • git merge: implement the changes you have fetched into your local files.

  • git pull: git fetch + git merge. However, it is recommended that you fetch first, check that you want to implement the changes, and then merge.

  • git push: upload your commits to a remote repository (like GitHub!)