Git

Basics

git config # Set user-specific configuration values like email, username, editor, etc
git clone # Clone a repository into a new directory
git init # Create an empty Git repository

git add # Add files for staging
git rm # Remove files from the working tree and from the index
git status # Show changes staged for next commit
git diff # Show changes between commits, commit and working tree, etc
git show # Show information about any git object
git log # Show commit logs
git bisect # Use binary search to find the commit that introduced a bug

git commit # Record changes to the repository
git branch # List, create, or delete branches
git checkout # Switch to another branch
git merge # Join two or more branches together
git rebase # Reapply commits on top of another base tip
git reset # Reset current HEAD to the specified state
git stash # Stash the changes in a dirty working directory away
git tag # Create, list, delete or verify a tag object signed with GPG

git remote # View all remote
git fetch # Fetch all objects from the remote repository that don’t currently reside in the local working directory
git pull # Merge all the changes present in the remote repository to the local working directory
git push # Update remote with committed changes

Useful options

git log --oneline # Display single commit information per line
git rev-list HEAD --count # Total number of commits
git shortlog # Summarize `git log` output
git commit --amend -m "New commit message" # Edit the last commit message

Miscellaneous

• Remove a file from history

  $ git filter-branch --force --index-filter \
    "git rm --cached --ignore-unmatch PATH-TO-YOUR-FILE-WITH-SENSITIVE-DATA" \
    --prune-empty --tag-name-filter cat -- --all

• Get a list of the deleted files in history

  ## without commit hashes
  git log --diff-filter=D --summary | grep delete
  
  ## with commit hashes
  git log --diff-filter=D --summary | grep -E 'delete|^commit\s+\S+'

• Amend older or multiple commit messages

  • Display a list of the last n commits in the default text editor

    git rebase -i HEAD~n

  • Replace pick with reword before each commit message you want to change, save and close the commit list file.

  • In each resulting commit file, type the new commit message, save the file, and close it.

  • Push the amended commits.

    git push --force

• Amend the very first commit message [*]

  git rebase -i --root

• Squash all previous commits into one [*]

  git reset $(git commit-tree HEAD^{tree} -m "A new start")

• See the diff for a commit [*]

  git show <commit> # or one of these
  git show --color --pretty=format:%b <commit>
  git diff-tree -p <commit>

• Print a leaderboard of authors based on number of commits in a repository

  git log --format='%aN' | sort | uniq -c | sort -nr
  git log --format='%aN' | sort -u # Print all contributors in alphabetical order

• Working with multiple GitHub accounts with SSH [*]

  • Create a new SSH key and add it to GitHub account #2. Save the private key file as something like id_rsa_2.

  • Update the SSH config:

    .ssh/config

    # Default GitHub
    Host github.com
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_rsa
    
    # GitHub account #2
    Host github-alt
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_rsa_2

  • When pushing to GitHub account #2, change the remote to reflect the new host:

    # git remote add origin git@github.com:username/repository.git
    git remote add origin git@github-alt:username/repository.git
    git push origin main