Git and Eclipsehttp://eclipse.org/egit

Stefan Lay (SAP)stefan.lay@sap.com

Matthias Sohn (SAP)matthias.sohn@sap.com

Twitter: @stefanlay, @masohn

+ =

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Git at Eclipse

Git is a Distributed Version Control System

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 is still beta and we want to establish a feedback loop to improve the tooling.

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Gerrit Code Review

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

Also serves as a central git server adding access control and workflow

Used by Android, JGit/Egit, …

Git at Eclipse | © 2010 by S. Lay and M. Sohn

History JGit/EGit2005    Linus Torvalds starts Git

2006    Shawn Pearce starts JGit

2009    Eclipse decides on Git           JGit/EGit move to eclipse.org           SAP joins

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 Planned 0.9 (Helios SR1)            Merge, Synchronize View, .gitignore

Git vs. CVS/SVN

• Distributedo Each user has full history

o Ability to work off-line

o Fast

o Rebase patches easily

o Forks happen, deal with it

o Powerful merging allows to use lots of branches

• Centralizedo --

o --

o Slow

o Patches go stale

o Forks are painful

o Merging is painful

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Git in OS and inside a company

• Git was invented for OpenSource project: Linux kernel developmento Distributed versioning has benefits for contributors in

OS development model

• Committer / contributor model can also be beneficial inside a company

• Git and Gerrit enable code review workflow

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Code Review – Why ?

Good means to improve quality

Cooperate to make changes perfect

Helps learning and avoiding silos

The way to get contributions from new contributors integrated without risk

Helps to discuss drafts on source code level beforethey reach master

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Code Review - Workflow

• Review every change• Authors can explicitly invite

reviewers• Look at the change• Comment on how to improve it• Discuss in context of the change• Complex changes reviewed

by many• Discussion leads to new

improved change (sometimes we have 20 versions until submit)

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Code Review - Experience

• Review takes time (1 day … months) o Implies parallel workflow o Every team member should do reviews regularlyo Authors have to wait for the review to happeno Git & Gerrit help a lot here

o Small changes are much easier to reviewo A change should logically do one thing (not many)o Split big changes into series of digestible

changes (patch series)

o Commit message should explain Why o The What should be obvious from the code change

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Code Review – Lifecycle of a Change

Git at Eclipse | © 2010 by S. Lay and M. Sohn

aa

mastermaster

topictopic

11

• create local topic branch• commit change• push it for review• review• automated verification

Code Review – Lifecycle of a Change

Git at Eclipse | © 2010 by S. Lay and M. Sohn

cc

bb

aa11

22

mastermastertopictopic

33

aa

mastermaster

topictopic

11

• create local topic branch• commit change• push it for review• review• automated verification

• refine based on review• push new patchsets until review votes ok

Code Review – Lifecycle of a Change

Git at Eclipse | © 2010 by S. Lay and M. Sohn

cc

bb

aa11

22

mastermastertopictopic

33

aa

mastermaster

topictopic

11

• create local topic branch• commit change• push it for review• review• automated verification

• refine based on review• push new patchsets until review votes ok

cc

bb

aa11

22

mastermaster

topictopic

33

dd

• Submit may lead to server-side merge• or merge / rebase before push

No Free Lunch -- DEMO

The best way to learn Git is to use Git

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Conclusion

DVCS like Git are powerful

Git supports convenient branching and merging Git is very fast and scales wellGerrit enables a nice code review workflow

Git is the future SCM of Eclipse

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Git at Eclipse

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

http://git.eclipse.org/ hosts live Eclipse Git reposVirgo, Mylyn Review, ScalaModules, SWTBot …

http://dev.eclipse.org/git/index.html git mirrors for CVSRead-only copies kept up-to-dateCan clone with git:// or http://

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Resources

Ask questions on the EGit forum or egit-dev/jgit-dev lists

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

If you want comedy, watch Linus' talk at Googlehttp://www.youtube.com/watch?v=4XpnKHJAok8

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

Git at Eclipse | © 2010 by S. Lay and M. Sohn

Features EGit 0.9

git-addgit-add git-format-patchgit-format-patch git-shortloggit-shortlog git-relinkgit-relink git-rev-parsegit-rev-parse

git-amgit-am git-gcgit-gc git-showgit-show git-remotegit-remote git-show-branchgit-show-branch

git-archivegit-archive git-grepgit-grep git-stashgit-stash git-repackgit-repack git-verify-taggit-verify-tag

git-bisectgit-bisect git-initgit-init git-statusgit-status git-replacegit-replace git-whatchangedgit-whatchanged

git-branchgit-branch git-loggit-log git-submodulegit-submodule git-annotategit-annotate

git-bundlegit-bundle * git-merge* git-merge * git-tag* git-tag git-blame git-blame

git-checkoutgit-checkout git-mvgit-mv git-configgit-config git-cherrygit-cherry .gitignore.gitignore

git-cherry-pick git-cherry-pick git-notesgit-notes git-fast-exportgit-fast-export git-count-objectsgit-count-objects git daemongit daemon

git-cleangit-clean * git-pull* git-pull git-fast-importgit-fast-import git-difftoolgit-difftool * HTTP support* HTTP support

git-clonegit-clone git-pushgit-push git-filter-branchgit-filter-branch git-fsckgit-fsck * Mylyn integration* Mylyn integration

git-commitgit-commit * git-rebase* git-rebase git-mergetoolgit-mergetool git-get-tar-commit-idgit-get-tar-commit-id * Staging View* Staging View

git-describegit-describe git-resetgit-reset git-pack-refsgit-pack-refs git-helpgit-help * Synchronize View* Synchronize View

git-diffgit-diff git-revertgit-revert git-prunegit-prune git-merge-treegit-merge-tree History ViewHistory View

git-fetchgit-fetch git-rmgit-rm git-refloggit-reflog git-rereregit-rerere Repositories ViewRepositories View

* planned for next release, supported, partial, missing, irrelevant for EGit