Git Command Overview

Basic Terminology

A commit is a set of changes to the files tracked by your repository. This can include files added, files removed, and files changed.

To commit is to add a new commit to the repository history.

A repository (or repo) is a folder where you can specify files for git to track. In each repository, you can commit files and folders and have git remember what changes you have made. You can also push your changes so that people you’re working with can see them.

Getting Yourself a Git Repository

Creating a new, local repo:

$ mkdir <my-repo-name>
$ cd <my-repo-name>
$ git init

OR

git init <my-repo-name>

If you’re not starting a new project but are making changes to a project that already exists, it makes more sense to “clone” the repo - that means to download a copy of a git repository stored somewhere else.

Cloning a shared, upstream repo

# If your upstream is for example, a folder on AFS
$ git clone <path to bare> [optional directory to create]

# If your upstream is hosted online, like on GitHub
$ git clone https://example.com/my/repo [optional directory to create]

Now that you have a git repository on your computer, you will be able to examine the status of the git repository and make commits.

Making and Committing Changes

After creating, deleting, or editing some files, you can ask git to tell you which files have been modified since the last commit.

Finding the current state of the git repo:

$ git status

Get used to running this command often!

In order to commit a change or a set of changes, you must “stage” them first.

“Stage” a file’s changes (staging comes before committing):

# stage files by name
$ git add <file> [...]

# stage all files in current directory
$ git add .

# Stage all files
$ git add -A

It’s better to create many small commits rather than one big one, which is why it’s better to use the first version to stage specific files. This lets you create a commit corresponding to a specific change.

There’s even more you can do with the staging area - be sure to checkout the section on “More On The Staging Area” later on this page.

Sometimes you want to know not just which files you’ve changed and/or staged, but also what in the file was changed.

Seeing what I’ve changed:

$ git diff

Once you have staged all the changes you want for a commit, you can tell git to make a commit.

Committing a set of changes:

# if you've already run `git add`
$ git commit

# If you haven't run `git add`
$ git commit -a

# If you want to write a short commit message:
git commit -m

Now that you’ve made a commit, it will show up in git’s record of commits.

Checking the commit history

$ git log --pretty=oneline --abbrev-commit --decorate --graph --all
# Shorter to type, but without as much information:
$ git log

You will be using this command a lot too!

You can always check what the last commit changed.

Show the changes in the most recent commit:

$ git show -p HEAD

Sometimes you want to “undo” a commit. You can do this in git by reverting the commit. This creates a new commit that undoes all the changes of the commit.

Revert the changes a commit introduced:

$ git revert <commit hash>

Branches

If you’d like to make a lot of commits and keep them logically separate for a while, while still sharing them with other people, you can use branches. This is frequently used when adding a large feature to a project: you work on the new feature in a new branch, leaving the master branch clean for others (or yourself) to make bugfixes; then, when the new feature is stable, you merge it back into the master branch.

Creating a new branch and switching to it

$ git checkout -b <branchname>

(Yes, the naming of this command is kind of inane. It’s equivalent to running git branch <branchname> to create the branch, and then git checkout branchname to switch to it.)

Listing your branches

$ git branch

The one you are currently on will have a star next to it.

Switching branches

$ git checkout <branchname>

Now you can make changes and commit as usual on any new branch you create. At some point, you’ll want to merge the changes made on one branch to your “main” branch.

Merging branches

$ git merge <branchname>

This will merge the branch called “branchname” into your current branch. So if you want to merge “branchname” into the master branch, you should git checkout the master branch, then run git merge <branchname>. This will pull in all the changes from the branch into the master branch. You may have to resolve some conflicting changes by hand.

Pushing

Earlier on, you may have “cloned” your git repository from another place, like Github. So there you were downloading changes to a git repository. You can also upload changes, which we call “pushing”.

Sharing your changes with everyone

$ git push origin master

You may have to replace “origin” with the name of the upstream to which you want to push (if you cloned the repository, it will be “origin” by default). You may also have to replace “master” with the branch you want to push changes from.

There’s a trick you can do to shorten this command:

# Run this on your first push
$ git push -u origin master
# the same stipulation from above applies

# then run this on all subsequent pushes
$ git push

More On The Staging Area

So far, all of the commands discussed have dealt with the files in your directory (the “working tree”), the local repository, and possibly a remote repository. There is actually a fourth area where your changes can be stored, called the “index”, which is logically located between the working tree and the repository. The index is a sort of staging area for commits, giving you the ability to control and inspect exactly what will be included in a commit. When something is in the index, it is said to be “staged”.

To “stage” changes (to add changes from your working tree to the index), you can use various forms of the git add command.

• git add <files> - add the listed files to the index
• git add -p - interactively add “hunks” to the index. This examines all files tracked by the repository, detects the sections that have been modified, and lets you add sections of files individually.
• git add -p <files> - like git add -p, but only looks at the listed files.

You can examine the staged changes with git diff –cached.

If you have staged changes which you wish to remove from the index, the command git reset can remove them:

• git reset <files> - unstage all changes from the listed files.
• git reset -p - interactively remove staged hunks from the index.
• git reset -p <files> - probably what you expect
• git reset --mixed - unstage all changes in the index

Once you have modified the index to your liking, you can commit the staged changes with a simple git commit (no arguments!).

Troubleshooting

You can use the Git man page: man git to see an overview, or git help <command> to open the man page for each individual git command.