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Version Control

Version Control. CS 30700 These outstanding slides were created by Kevin Schenk, BS in Computer Science, Purdue University, 2012. What is version control ?.

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Version Control

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  1. Version Control CS 30700These outstanding slides were created by Kevin Schenk, BS in Computer Science, Purdue University, 2012.

  2. What is version control? • Version control (or revision control) is the term for the management of source files, and all of the intermediate stages as development proceeds. • A version control system is a repository of files. Every change made to the source is tracked, along with who made the change, etc. • Other items can be kept in a version control system in addition to source files -- Project Charter, Product Backlog, Design Document, Sprint Planning Document, Sprint Retrospective….

  3. Version Control Examples

  4. Why is version control important? • Version control allows us to: • Keep everything of importance in one place • Manage changes made by the team • Track changes in the code and other items • Avoid conflicting changes

  5. Features of Version Control • Reversion: If you make a change, and discover it is not viable, how can you revert to a code version that is known to be good? • Change/Bug Tracking: You know that your code has changed; but do you know who did it, when, and why? Sometimes this is where a bug was introduced? • Branches: How to introduce a completely new feature or concept and not mess up the working code? • Merging branches: If I divided the code, how to merge new code with good old code and not mess up

  6. Committing Code • Commit:the action of writing or merging the changes made in the working copy back to the repository • Trunk: The unique line of development that is not a branch (sometimes called the baselineor mainline) • Head: The most recent commit Main Trunk Apple Apple Orange Apple Orange Banana Apple Orange Strawberry Revision 1 Revision 2 Revision 3 Revision 4 (HEAD)

  7. Committing Code (SVN) • To add the file to the repository: • To check-in (commit) the file: • The -m flag is the message to use for this check-in. • Note: Subversion (svn) commands are described in http://www.yolinux.com/TUTORIALS/Subversion.html svn add list.txt svn ci list.txt –m “Changed the list”

  8. Checking Out & Editing Code Main Trunk Apple Orange Banana Check Out Apple Orange Strawberry Revision 3 Revision 4 Apple Orange Strawberry Revert Working Copy Check In (Commit)

  9. Checking Out Code (SVN) • To get the latest version: • To throw away changes: • To check out a particular version: svn checkout list.txt svn revert list.txt svn checkout –r2 list.txt

  10. Differences Main Trunk • Most version control systems store diffs rather than full copies of the file. This saves disk space. -Apple +Grape +Orange +Banana Apple Apple Orange Apple Orange Banana Orange Banana Grape svn diff –r3:4 list.txt Revision 1 Revision 2 Revision 3 Revision 4

  11. Branching Code • A set of files under version control may be branched (or forked) at a point in time so that, from that time forward, two (or more!) copies of a file may develop in different ways independently of each other. Apple Grape Apple Grape Cherry Revision 5 Revision 6 Branch Main Trunk Apple Grape Apple Grape Kiwi In SVN: svn copy /path/to/trunk /path/to/branch Revision 4 Revision 7

  12. Merging Code Apple Grape Apple Grape Cherry +Cherry Revision 5 Revision 6 Branch Main Trunk Apple Grape Apple Grape Kiwi Apple Grape Kiwi Cherry +Kiwi +Cherry Revision 4 Revision 7 Revision 8 In SVN: svn merge –r6:7 /path/to/branch

  13. Conflicts • A conflict occurs when different team members make changes to the same document, and the system is unable to reconcile the changes. A user must resolve the conflict by combining or manually editing the changes. Apple Grape Cherry Check In Revision 4* (Bob) Apple Grape Apple Grape Cherry Main Trunk Revision 4 Revision 5 Apple Kiwi Check In Conflict Revision 4* (Alice)

  14. Centralized vs. Distributed Version Control Systems

  15. Centralized Version Control Systems • Centralized version control systems are based on the idea that there is a single “central” copy of your project on a single server and programmers “commit” their changes to this central copy.

  16. Centralized Version Control Systems • Advantages • Easy to understand • Saves space – only one copy of each file • Disadvantages • Dependent on access to the server • Can be slow since every transaction requires a connection to the server

  17. Distributed Version Control Systems • Distributed version control systems do not rely on a central server to store all the versions of a project’s files. • Instead, every developer “clones” a copy of the repository and has a virtual copy of the full project on his/her own machine • Distributed systems are a newer option.

  18. Distributed Version Control Systems • Advantages • No server necessary – all actions are local . • Faster. • Disadvantages • A lot happens behind the scenes with some chance of undetected conflicts.

  19. Version Control Requirement in CS 30700 • Each team must use some version control system • Instead of turning in documents and code on BlackBoard, teams will simply commit their documents and code to their repository • Give your Project Coordinator access to view your repository and to track changes

  20. GitHub • GitHub is a web-based hosting service for software development projects that use the Git revision control system • GitHub <https://github.com> • GitHub offers free accounts for open source projects

  21. GitHub • GitHubDocumentation <https://help.github.com> • GitHub is the most popular open source code repository site • We suggest you use GitHub to gain experience with it • Employers, startups, and hackathons increasingly use Github

  22. Bitbucket • Bitbucket is a web-based hosting service for projects that use either the Git or Mercurial revision control systems • Bitbucket<https://bitbucket.org> • Bitbucket Free Academic Accounts <http://blog.bitbucket.org/2012/08/20/bitbucket-academic> • Bitbucket Documentation <https://confluence.atlassian.com/display/BITBUCKET/Bitbucket+Documentation+Home>

  23. Version Control References • Subversion (SVN) - http://subversion.apache.org • TortoiseSVN (Windows) - http://tortoisesvn.tigris.org • Concurrent Version Systems (CVS) - http://savannah.nongnu.org/projects/cvs • Git - http://git-scm.com • TortoiseGit(Windows) - http://code.google.com/p/tortoisegit • Mercurial - http://mercurial.selenic.com • RabbitVCS(Linux) - http://www.rabbitvcs.org

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