egit and gerrit code review - eclipse democamp bonn - 2010-11-16

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EGit & Gerrit Code Review Towards Contributor's Heaven http://eclipse.org/egit http://code.google.com/p/gerrit/ Matthias Sohn (SAP) [email protected] + =

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Presentation on EGit and Gerrit Code Review held at Eclipse DemoCamp Bonn Nov 16, 2010

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Page 1: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

EGit & Gerrit Code ReviewTowards Contributor's Heaven

http://eclipse.org/egithttp://code.google.com/p/gerrit/

Matthias Sohn (SAP)[email protected]

+ =

Page 2: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Git… a distributed revision control system built by the Linux project to automate patch workflow

Distributed means no central repository• No central authority!• Easy offline usage• Easy to fork a project• Protected against manipulation by cryptographic hashes

Really good at merging• Coordination only needed "after the fact”• Easier to rejoin (or refresh) forked projects

Structured around commits (i.e. patches)• Integrates with email channel• Tools for identifying problem commits (git bisect)• Tools for restructuring branches w/ specific commits

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 3: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Git at Eclipse

Eclipse defined a roadmap to move to Git in 2009CVS is deprecated; SVN will be deprecated in the future

EGit is an Eclipse Team provider for Git http://www.eclipse.org/egit/

JGit is a lightweight Java library implementing Git http://www.eclipse.org/jgit/

The goal is to build an Eclipse community around Git EGit and JGit are still beta and we want to establish a feedback loop to improve the tooling

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 4: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

History of JGit and EGit2005 Linus Torvalds starts Git

2006 Shawn Pearce starts JGit

2009 Eclipse decides for Git Roadmap JGit/EGit move to eclipse.org

3/2010 Released 0.7 (first release at Eclipse) Diff/Merge Algorithms, Automatic IP Logs

6/2010 Released 0.8 (Helios) Usability Improvements, Git Repositories View, Tagging

9/2010 Released 0.9 (Helios SR1) Merge, Synchronize View, .gitignore

Planned: 12/2010 0.10 (Helios SR2) 3/2011 0.11 6/2011 1.0 (Indigo)

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 5: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

What is Peer Code Review?

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

… best an integral part of coding process

Debugging someone else's broken code... involuntary code review, not so good

Guido van Rossum [1]

[1] http://code.google.com/p/rietveld/downloads/detail?name=Mondrian2006.pdf

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 6: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Code Review – Benefits

Four eyes catch more bugs

Coding standards help readability → better code

Mentoring of new developers

Establish trust relationships

Good alternative to pair programming

Guido van Rossum [1]

[1] http://code.google.com/p/rietveld/downloads/detail?name=Mondrian2006.pdf

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 7: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Code Review @ Eclipse in Bugzilla

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 8: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Eclipse – Review Process

Contributors • create patch using CVS, SVN, Git• attach patch to bug in Bugzilla

Committers • do code and IP review in Bugzilla• initiate IP review for changes > 250 loc• commit accepted changes

IP Team• does IP reviews

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 9: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Gerrit Code Review

Gerrit is a Code Review system based on JGit http://code.google.com/p/gerrit/

Also serves as a git server adding access control and workflow

Used by • Android https://review.source.android.com/• JGit, EGit http://egit.eclipse.org/r/• Google, SAP, …

Eclipse wants to use it …

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 10: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Gerrit

http://egit.eclipse.org/r/ - change,825Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 11: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Gerrit Workflow

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 12: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Code Review – Our Experience

• Review all changes!

• Review takes time (1 day … weeks)

• Implies parallel workflow

• Every team member should do reviews regularly

• Authors have to wait for the review to happen

• Git & Gerrit help a lot here

Code Review | © 2010 by M. Sohn

Page 13: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Demo: Using EGit and Gerrit Code Review

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 14: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Conclusion

EGit and JGit are evolving quickly

Gerrit enables a nice code review workflow

Git supports convenient branching and merging

Git is very fast and scales well

Eclipse and major other OS projects are moving to Git

Git and Gerrit kick ass!

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 15: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Git Resources

http://git-scm.com/documentation is your friend

Watch Linus' talk at Googlehttp://www.youtube.com/watch?v=4XpnKHJAok8

Read the Pro Git book - http://progit.org/book/

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn

Page 16: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Features EGit 0.10

git-add git-format-patch git-shortlog git-relink git-rev-parse

git-am git-gc git-show git-remote git-show-branch

git-archive git-grep git-stash git-repack git-verify-tag

git-bisect git-init git-status git-replace git-whatchanged

git-branch git-log git-submodule git-annotate

git-bundle * git-merge * git-tag * git-blame .gitignore

git-checkout git-mv git-config git-cherry git daemon

git-cherry-pick git-notes git-fast-export git-count-objects Visual merge tool

git-clean  git-pull git-fast-import git-difftool ** HTTP support

git-clone git-push git-filter-branch git-fsck * Mylyn integration

git-commit ** git-rebase git-mergetool git-get-tar-commit-id * Staging View

git-describe git-reset git-pack-refs git-help * Synchronize View

git-diff git-revert git-prune git-merge-tree History View

git-fetch git-rm git-reflog git-rerere Repositories View

** planned for 0.10, * planned for 0.11 supported, partial, missing, irrelevant for EGit

Page 17: EGit and Gerrit Code Review - Eclipse DemoCamp Bonn - 2010-11-16

Git at Eclipse

EGit and JGit developed at http://egit.eclipse.org

http://git.eclipse.org/ hosts live Eclipse Git repos

http://dev.eclipse.org/git/index.html git mirrors for CVSRead-only copies kept up-to-date

Using Git in Eclipse | © 2010 by C. Aniszczyk and M. Sohn