Version Control Systems (VCS)

• Tools that can register any change in any file or set of files over time
• They let us:
  • Recover any older version
  • Compare files over time
  • Determine who changed the file
  • ...

Local VCS

• Create backup of a project and store changes locally
• Advantage: simplicity
• Drawback: manual management (error prone)

Local VCS

Centralized VCS (CVCS)

• Create backup of a project and store changes in a remote server
• Many clients can connect to server and share their work
• Advantage: improves team work
• Drawback: if server fails, everything is lost

Centralized VCS (CVCS)

Distributed VCS (DVCS)

• Create backup of a project and store changes in a remote server
• Many clients connect to server and download the whole project
• Advantages:
  • Improves team work
  • If server fails, any client has a copy to restore

Distributed VCS (DVCS)

Git

• DVCS created by Linux team to solve their own version control problems
• Features:
  • Speed
  • Easy design
  • Allows branches (non-lineal development)
  • Suitable for big projects

Git data modeling

• Git stores snapshots of the project's filesystem
• With every change, Git only stores the new files changed, not the whole project
  • For the rest of files, it just "points" to previous version

Git data modeling

Other Git fundamentals

• Local work: many tasks are performed locally, which is faster, and lets us work with the project even without Internet connection
• Integrity: Git uses a SHA-1 algorithm to store information (data is always verified)
• Information addition: Git never removes anything, it only adds information. We can undo everything

Git project states

Every file in a project is in one of these three states:

• Modified: data has been changed locally, but it has not been committed yet.
• Staged: data has been tagged to be sent in next commit.
• Committed: data is safely stored in a local storage

Git sections

There are 3 sections in Git project:

• Git directory: metadata and database of the elements of the project.
• Working directory: files extracted from the Git database, ready to be used.
• Staging area: contains information about the files that will be sent in next commit.
  • Also called index

Git sections