Presentation held at Eclipse democamp Vienna on 2012-12-02

1. Eclipse Hacker’s
Matthias Sohn
(SAP)matthias.sohn@sap Guide to the
.com
twitter: @masohn
Git Universe
Developing with EGit and Friends
http://eclipse.org/jgit
http://eclipse.org/egit
http://code.google.com/p/gerrit
background photo courtesy of Eclipse Hacker’s Guide to the Git Universe | ©
NASA http://www.nasa.gov/multimedia/guidelines/index.html 2011 by M. Sohn

2. Git
… a distributed revision control system built by the
Linux project to facilitate code review
Distributed means no central repository
• No central authority!
• Easy offline usage
• Easy to branch a project
• Protected against manipulation by cryptographic hashes
Really good at merging
• Coordination only needed "after the fact”
• Easier to rejoin (or refresh) branches
Structured around commits (i.e. patches)
• Tools for identifying problem commits (git bisect)
• Tools for restructuring branches w/ specific commits
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

3. Git is mature and popular
… Git is widely used and is the most popular
distributed version control system
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

4. Git use is growing
Google trend search in US:
http://aniszczyk.org/2011/11/23/apache-and-politics-over-code/
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

5. History Git @ Eclipse
2005 Linus Torvalds starts Git
2006 Shawn Pearce starts JGit
2009 Eclipse decides on Git as replacement for CVS/SVN
JGit/EGit move to eclipse.org, SAP joins
3/2010 EGit 0.7 (first release at Eclipse)
9/2011 EGit 1.1 (Indigo SR1)
12/2011 Eclipse Git adoption:
EGit 1.2
Gerrit hosted by Eclipse
12/2012 Eclipse will retire CVS
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

6. Why did Eclipse move?
Git increases developer productivity
Git makes collaboration easier
Gerrit Review is great for Contributors
Github is the most popular coding platform
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

7. Git in Java
JGit is a lightweight Java library implementing Git
• http://www.eclipse.org/jgit/
EGit is an Eclipse Team provider for Git based on JGit
• http://www.eclipse.org/egit/
Gerrit Code Review is a Git server based on JGit
• permissions and review workflow
• http://code.google.com/p/gerrit
Gitblit is a Git server based on JGit
• browsing (like GitWeb), statistics and RSS feeds
• http://code.google.com/p/gitblit/
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

8. Github
• Became largest Forge
• Free for public repositories
• EGit has GitHub connector
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

9. Modern Code Review – What is it ? Guido van Rossum [1]
When one developer writes code, another
developer is asked to review that code
A careful line-by-line critique
Happens in a non-threatening context
Goal is cooperation, not fault-finding
Integral part of coding process
Otherwise this will happen:
Debugging someone else's broken code
– Involuntary code review: Not so good; emotions may flare
[1] http://code.google.com/p/rietveld/downloads/detail?name=Mondrian2006.pdf
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

10. Code Review – Benefits Guido van Rossum [1]
Four eyes catch more bugs
o Catch bugs early to save hours of debugging
Mentoring of new developers / contributors
o Learn from mistakes without breaking stuff
Establish trust relationships
o Prepare for more delegation
Good alternative to pair programming
o asynchronous and across locations
Coding standards
o Keep overall readability & code quality high
[1] http://code.google.com/p/rietveld/downloads/detail?name=Mondrian2006.pdf
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

11. Gerrit
Gerrit Code Review
git git
git git
master
change 12
submit accepted
change 10 change 12
change 23
push improved fetch change 23
fetch master
change 10 to try it
to get
updates
Developer PC Developer PC
git git
git git
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

12. Integration with EGit
Gerrit is a Git server
o any Git implementation can work with Gerrit
EGit simplifies work with Gerrit
o fetching a change
o automatic "push to Gerrit" configuration
Mylyn Reviews has a Gerrit connector
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

13. Gerrit - Workflow
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

14. Gerrit Review UI
http://egit.eclipse.org/r/#change,825
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

15. Gerrit – Eclipse Integration
Mylyn Gerrit Connector
• Task list integration
• Review editor,
inline comments
• Publishing reviews
• EGit integration for fetching changes in review
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

16. DEMO
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

17. Conclusion
DVCS like Git are powerful
Git supports convenient branching and merging
Git is very fast and scales well
Gerrit enables a nice code review workflow
Code review rocks !
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn

18. Q&A
Eclipse Hacker’s Guide to the Git Universe | © 2011 by M. Sohn