Git

Git
An Introduction to Version Control

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Introduction

The Important Pieces

Repositories:
- A repository is an "official" archive
Working Trees:
- A working tree is a directory/folder on a filesystem (with an associated repository)
Index:
- An intermediate collection of changes (that need to be confirmed) before they can be committed (i.e., moved from the working tree to the local repository)

Normal "Centralized" Work Cycle - Getting Started

Create the Central Repository:
- Often handled by a third-party hosting services
Clone the Central Repository:
- Each developer uses the git clone command

Normal "Centralized" Work Cycle - Day-to-Day

Using the Local Repository:
- If necessary (e.g., if switching branches), use git checkout to update the working tree to match a specific tree in the repository
- Make changes to the documents in the working tree
- If necessary, add new files to the index using git add
- Commit to the local repository from the index using git commit
Pushing New Commits to the Central Repository:
- Attempt to update the central repository using the git push command
- In the event of potential conflicts that result from someone else pushing before you (i.e., "non-fast-forward" errors)
  - Use the git pull command (which does both a git fetch and git merge) to incorporate the changes that others have made
  - Resolve any actual conflicts
  - Use git push to update the central repository

Normal "Centralized" Work Cycle - Day-to-Day (cont.)

An Important Objective:
- Reduce the number of conflicts that must be resolved when pushing later in the day
One Way to Achieve this Objective:
- Perform a git pull (and resolve any conflicts) at the start of the day
What This Accomplishes:
- It makes sure that you have the most recent code pushed by your teammates before you start making more changes

Other Work Cycles

Some Examples:
- Feature Branching - all feature development takes place in a dedicated branch (not the master branch)
- Gitflow - a strict branching model designed around project releases
- Forking - Every developer has a server-side repository
Issues:
- Longer-lived branches are riskier
- The work cycle should allow for easy reversions (because things do go wrong)

Nerd Humor

(Courtesy of xkcd)