Appendix B — Glossary of Commands

B.1 Git

  • git init initializes a new Git repository in the current working directory.

    • git init [DIRECTORY] like above, but in the specified directory.

  • git add [FILE] tracks changes in the specified file, but does not commit those changes.

    • git add . tracks changes in all files in the current directory and all subdirectories. Be careful not to track changes you didn’t intend!

  • git commit -m "[MESSAGE]" commits all tracked changes to the repository with a specified message. Remember the quotes around the message!

    • git commit is like the above, but uses the default text editor (probably vim). You can exit that editor by typing :cq and hitting enter. If that fails, you may want to kill your terminal and restart.

  • git status shows the state Git thinks the repository is currently in. By default it shows what branch you’re on, staged and unstaged changes, and untracked files.

  • git log shows the history of the git repository. If the history is longer than your current terminal screen, you can navigate history with the arrow keys. Hit q to quit.

    • git viz is an alias we made for this class that shows the commit history in an easier-to-read format.

  • git config manages local (for one repository) and global (for all repositories on your computer) configuration. These can change many aspects of how Git functions. Most functionality offered by this command is not part of this class.

    • git config --global alias.[NAME] "[COMMAND]" creates a new global subcommand for git that executes the passed command named NAME. This is how we made git viz.

  • git diff [COMMIT_1] [COMMIT_2] shows the changes from COMMIT_1 to COMMIT_2.

    • git diff HEAD~1 HEAD shows the differences from HEAD~1 to HEAD
    • git diff HEAD HEAD~1 shows the inverse from the above, so all changes are shown as negated (adds become removes and vice versa).

  • git checkout [COMMIT] unloads the currently-loaded commit and loads the specified one. COMMIT can may be a tag, like the name of a branch (main) or a commit hash.

    • git checkout - checks out the previously-checked out commit/branch.
    • git checkout -b [BRANCH] checks out BRANCH, or creates one if it did not already exist.

  • git branch [BRANCH] creates a new branch called BRANCH.

    • git branch lists all branches in the repository.
    • git branch -d [BRANCH] deletes the branch BRANCH, if it has already fully merged.
      • git branch -D [BRANCH] forces BRANCH to be deleted, regardless of if it has been merged.

  • git restore --staged [FILE] unstages all changes for FILE, meaning git commit won’t commit changes to that file.

    • git restore [FILE]

  • git revert [COMMIT] --no-edit tries to revert any changes COMMIT made to the repository and automatically creates a new commit. The command will let you know if it was unable to automatically revert the commit. The --no-edit indicates you don’t want to write a custom commit message for the revert commit.

  • git merge [BRANCH] tries to apply all commits from when [BRANCH] diverged from the current branch until the most recent commit on that branch. If there are merge conflicts, you need to resolve those commit-by-commit and enter git merge --continue until it completes. Does not edit the target branch (the one you specify). So if you are on a branch named main and run git merge docs, Git will try to add all of the missing commits from docs to main, but leave docs untouched.

    • git merge --abort aborts the current merge process. This is useful if you’ve accidentally started a merge, or otherwise need to exit unexpectedly.

B.1.1 Referencing commits

  • HEAD is a special reference that indicates the current commit you are at in the repository. This changes when you git checkout, git commit, or do anything that changes
  • HEAD~[N] references N commits before HEAD. So HEAD~0 is equivalent to HEAD, HEAD~1 is the commit before HEAD, HEAD~2 is two commits before HEAD, and so on.
  • The ~N format also works for branches, so main~3 references three commits before the most recent commit to the main branch.
  • You can always reference a commit by its hash, the letters and numbers to the right of commit messages in git viz and git log. If manually typing, you just need the first four characters, so if git log shows 879798e you can just type 8797, but copying is usually easier.

B.1.2 Git Config

You’ll want to use these so git commit doesn’t complain about you not having set these up. If you intend to use different names/emails in Git repositories on the same computer, omit --global and make sure to run these from the repository you want to use these in. When choosing which email to use, think of it as “If someone had a question about this change, how would I want them to contact me?”

  • git config --global user.name "Your Name" sets the human-readable name in your git commits in all repositories on your computer to that name.
  • git config --global user.email "you@example.com" does the same, but for your email.

B.2 Command Line Tools

For many of these commands, if you type --help after the command, it will print out detailed documentation.

  • pwd, shows the path to your current working directory.
  • ls, lists the contents of your current directory.
  • cd [DIRECTORY], changes the directory you’re in.
    • cd .., moves to the parent directory of the current working directory.
    • Paths starting with / indicate absolute paths rather than ones relative to your working directory.
    • cd - moves to the directory you were previously in.
  • mkdir, makes a new directory.
  • touch, creates a new (empty) file.
    • The command has other uses, but those aren’t part of this class.
  • rm, removes files and directories.

B.2.1 Terminal Advice

  • Accessing previous commands - You can navigate through your previous commands by hitting the up and down arrow keys.
  • Clearing your terminal - You can clear your terminal with CTRL+L or by entering the command clear.

B.2.2 Optional Commands

These are not required for this course, but you might find them useful.

  • printf "1. This is the first line\n2. This is the second line." >> file.txt appends text to a file, creating the file if it does not already exist. If you search online you may also see echo instead of printf, but echo can’t easily write multiple lines at once.
  • clear clears your terminal of all input.