Software Engineering in Practice Version Control Systems 

A typical scenario 

Version control systems – Why? • Clutter free workspace (no numbered files) • Avoids duplication • Backup and restore • Synchronization • Undo • Track changes (with messages) • Track ownership • Merging and branching • Collaboration 

VCS – History (1) Gen. Networking Operations Concurrency Examples 1 None One file at at time Locks SCCS, RCS 2 Centralized Multi-file Merge before commit Subversion, TFS, CVS 3 Distributed Change- sets/ snapshot Commit before merge Git, Bazaar, Mercurial http://ericsink.com/vcbe/html/history_of_version_control.html 

VCS – History (2) http://www.iiis.org/cds2011/cd2011imc/iceme_2011/paperspdf/fb394vz.pdf SCCS by Marc J. Rochkind at BellLabs 1972 1980 RCS by Walter F. Tichy at Purdue Univ. 1985 CVS by Dick Grune at Vrije University 1992 ClearCase by Atria (later IBM) 1994 Visual SourceSafe by Microsoft 2000 Subversion by Karl Fogel 2005 Git by open-source community TFS by Microsoft 

Let’s understand Git 

Git basics (1) • Snapshots (and not change-sets) CVS, Subversion, and others Git 

Git basics (2) • Local operations • Majority of operations are local - commit, log, branch... • Integrity • Impossible to change contents without Git knowing about it. • 40 char SHA-1 hash 

Git basics (3) • Stages • Committed • Staged • Modified http://rogerdudler.github.io/git-guide/ https://git-scm.com/book/en/v2/Getting-Started-Git-Basics 

Git Terminology 

Terminology Repository The database storing the project files. 

Terminology Commit (or check-in) The act of saving a working copy (a workfile or set of workfiles) to your repository. 

Terminology Head (or tip) The latest version in a branch. 

Terminology Branch A branch is a parallel version of a repository. http://rogerdudler.github.io/git-guide/ 

Terminology Clone A clone is a copy of a repository that lives on your computer instead of on a website's server. 

Terminology Diff A diff is the difference in changes between two commits, or saved changes. 

Terminology Fork A fork is a personal copy of another user's repository that lives on your account. 

Terminology Merge Merging takes the changes from one branch (in the same repository or from a fork), and applies them into another. 

Terminology Pull Pull refers to when you are fetching in changes and merging them. 

Terminology Pull Request Pull requests are proposed changes to a repository submitted by a user and accepted or rejected by a repository's collaborators. 

Terminology Push Pushing refers to sending your committed changes to a remote repository such as GitHub.com. 

Let’s get our hands dirty 

Installation https://git-scm.com/downloads 

Commands Create a repository git init 

Commands Clone a repository git clone 

Commands Add a file to repository git add 

Commands Commit git commit –m “description” 

Commands Pull changes git pull 

Commands Push changes git push 

Commands Merge changes git merge 

Commands See log git log 

Commands See git repository status git status 

Let’s get our hands dirty … actually 

Now what? … Practice https://try.github.io/levels/1/challenges/1 

Assignment Taksidiotis – Athens travel guide by the Greeks Tasks • Clone the repo – [email protected]:tushartushar/taksidiotis.git • Add an interesting place (such as museum, bar, or restaurant), activity (walking tour, or food/wine-tasting tour), or anything interesting for a tourist to the guide.md file • Contribute to at least 3 categories • The important thing is – you, as a Greek, are recommending it • You may change/modify text added by others • Try to arrange the entries in categories (such as ‘Tour’, ‘Food’, ‘History’, and ‘Islands’) • Commit your changes • Push to the GitHub repo • Deadline – 5 PM, Feb 28, 2018 

Courtesy: spikedmath.com Thank you