Version Control

ITEC 3870 Software Development II,
Anca Doloc-Mihu and Cengiz Günay

(License: CC BY-SA 4.0)

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Why Version Control?

It’s a must in today’s computing industry
- Mt. Gox, a company that don’t use VC and lost almost a billion dollars…
- Another painful story without VC
- challenge: find more horror stories!
You can even version control documents, class files, financial files, …
Also called source control, code management, concurrent versioning, revision control, …

Advantages:

Track changes, keep logs of past development
Automatic backups/safety net
Concurrent versions: XP vs. Win8
Allows teamwork

Teamwork on the same codebase: How?

Seriously, how?

Teamwork: No control? Overwrite chaos!

Teamwork: Locking

Teamwork: Merging

Merging example

Each commit increments version

Github for version control

`git` is the program behind Github

Common usage scenario:

git clone gets working copy from repo
Make changes in local working copy
git add <files...> to select your changed files
git commit saves your changes into the version control history with a comment (Wash, rinse, and repeat step 2. Commit often!)
git push publishes your previous commits to remote repository (Github)
git pull receives latest changes from repo to sync

Useful commands: Investigating the past

git diff shows your changes from last repo version
git log [filename] lists all commits, optionally those touching a filename
git diff <commit> shows changes in version labeled as <commit>
git checkout <commit> rewinds all files back to a version

Challenge: How to find a bug

You have been messing with the code
Suddenly you realized you broke the program
How do you find when was the bug introduced?

Hint: use git checkout <commit>

Parallel development: branches and merging

Many ways to do it, but recommended way:

master or main for releases
develop for active development
Optional: open one branch per feature, e.g. feature-xyz

Relevant Git commands:

git switch xyz for switching all your code to branch xyz (without losing if you committed all)
git merge xyz for merging all the changes in branch xyz onto current branch
resolve conflicts (see your assignment)

Common issues with Git

Avoiding bloating and conflict hell:

The .gitignore file: Add lines of file patterns to be kept out of your repo.

Mac vs PC guy: different line endings:

Can create a lot of trouble when sending/receiving files between Mac/Linux and Windows
Git has settings for it: core.autocrlf will automatically convert for you!

Removing already deleted files from your repo:

git add -u files...

Highly recommended visual interface:

SourceTree
Visual Studio Code plugin for Git

Git Resources

Credits

Opening comic from Return to Zero by EEworldonline.com