Git and GitHub

Diff and Patch

diff

diff is used to find differences between two files. For easier usage, combine it with -u:

diff -u file1 file2

diff -u

Compares two files line by line, displaying the differences side by side:

diff -u original.txt updated.txt

patch

patch applies file differences to another file. Example:

1. Save differences as a .diff file:

   diff -u original.txt updated.txt > changes.diff

2. Apply the patch:

   patch original.txt changes.diff

References

• diff man page
• patch man page

Git Basics

Initial Setup

git config --global user.name "Your Name"
git config --global user.email "[email protected]"
git config -l  # Check current configuration

GPG Signing

Enable GPG signing for commits to enhance security:

1. Generate a GPG key:

   gpg --full-generate-key

2. Add your GPG key to Git:

   gpg --list-secret-keys --keyid-format=long
   git config --global user.signingkey <key_id>
   git config --global commit.gpgsign true

3. Export your GPG key for public sharing:

   gpg --armor --export <key_id>

4. Verify GPG signing with:

   git commit -S -m "Your message"

Creating a Repository

git init  # Initialize a new repository
git add file.txt  # Add a file to the staging area
git rm file.txt  # Remove a file from the repository

Committing Changes

git commit  # Commit changes (opens a text editor for the message)
git commit -m "Your commit message"  # Commit with a message inline
git commit -a  # Stage tracked changes and commit them in one step
git commit --amend  # Modify the last commit

Checking Status and Logs

git status  # Show the status of the working directory
git log  # View commit history
git log -p  # Show commits with changes (patch format)
git log --graph --oneline --all  # View commit tree in one line
git log --stat  # Display added/deleted statistics per file

Viewing Changes in Other Branches

git diff <branch1> <branch2>  # Compare two branches
git diff <branch>:<file>  # Compare a file from another branch

Differences

git diff  # Show differences between working directory and index
git diff --staged  # Show differences between staged files and last commit
git add -p  # Interactively choose changes to stage

Undoing Changes

git reset HEAD <file>  # Unstage a file
git reset -p  # Interactively reset changes
git revert <commit_id>  # Create a new commit to undo a previous one
git commit --amend  # Amend the last commit

Using Remote Repositories

Cloning and Synchronizing

git clone <URL>  # Clone a remote repository
git pull  # Fetch and merge changes from the remote repository
git push  # Push commits to the remote repository

Managing Remotes

git remote -v  # View configured remotes
git remote show origin  # View details of a remote repository

Branches

Managing Branches

git branch  # List branches
git branch <name>  # Create a new branch
git branch -d <name>  # Delete a branch
git branch -D <name>  # Force delete a branch

Switching and Merging

git checkout <branch>  # Switch to a branch
git checkout -b <branch>  # Create and switch to a new branch
git merge <branch>  # Merge a branch into the current branch
git merge --abort  # Abort a merge in case of conflicts

Viewing Branch History

git log --graph --oneline  # View branch commit history in graph form
git branch -r  # List remote branches

SSH and Credentials

Setting Up SSH

• Generating an SSH key
• Caching GitHub password

Other Useful Commands

Moving and Renaming Files

git mv <old-name> <new-name>  # Rename or move a file

Fetching Updates

git fetch  # Download changes from the remote repository

Skipping the Staging Area

git commit -a -m "Message"  # Stage and commit in one step