Lecture Notes on Version Control Systems and Git

General Information

• Office Hours:
  • Open to questions from any lecture or related topics.
  • Held in 32 G9 lounge (Gates tower, 9th floor).

Introduction to Version Control Systems

• Definition: Tools used to track changes to source code or files/folders.
• Collaboration: Facilitates working with others on software projects.
• Snapshots: Track changes as a series of snapshots, each capturing the entire state of a folder.
• Metadata: Includes author info, commit timestamps, and messages.

Uses of Version Control

• Individual Use: Review old code, understand changes via commit messages, avoid conflicts with branching.
• Collaboration: Resolve conflicts, send code patches, track authorship and changes.
• Powerful Features: Identify when a regression was introduced using tools like Git's binary search.

Introduction to Git

• Reputation: Known for a complex interface; better understood by learning the data model first.
• Data Model: Understanding Git’s internals helps to understand commands.

Git Data Model

• Files and Folders: Modeled as trees (folders) and blobs (files).
• History Modeling: Uses a directed acyclic graph (DAG) instead of a simple linear sequence.
• Snapshots (Commits): Contain parents, metadata, and the snapshot’s top-level tree.
• Object Storage: Objects (blobs, trees, commits) are content-addressed using a SHA-1 hash.
• References: Map human-readable names to SHA-1 hashes; allow referring to snapshots by name.

Basic Git Commands

• Git Init: Initialize a new Git repository.
• Git Status: Show the current state/status of the repository.
• Git Add: Stage changes for the next commit.
• Git Commit: Record a snapshot of staged changes.
• Git Log: View the version history.
• Git Checkout: Move between different snapshots/branches.
• Git Diff: Compare changes between commits or working directory.

Branching and Merging in Git

• Branches: Allow parallel development on different features.
• Git Branch: Create and list branches.
• Git Merge: Combine changes from different branches.
  • Merge Conflicts: Occur when changes are not automatically compatible; need manual resolution.

Git Remotes

• Definition: Copies of the repository that are hosted elsewhere (e.g., on GitHub).
• Git Push: Send changes from local to remote.
• Git Fetch: Get changes from remote to local.
• Git Pull: Fetch and merge changes from remote.

Additional Tools and Concepts

• Git Config: Customize Git settings using configuration files.
• Git Add -p: Interactive staging for commits.
• Git Blame: Identify who modified each line in a file.
• Git Stash: Temporarily store changes not ready for a commit.
• Git Bisect: Automatically find when a bug was introduced by searching commit history.

Resources

• Pro-Git Book: Recommended for further learning.
• Exercises: Available for practice and deeper understanding.
• Graphical Clients & Plugins: Explore additional Git interfaces and editor integrations.

This summary covers the main topics discussed in the lecture, providing a foundational understanding of version control systems and Git. For more in-depth exploration, refer to recommended resources and exercises.