Migrating to DVCS: Why You should do it and how Atlassian's tools can help
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Presentation CB6 at the 2011 Atlassian Summit
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Migrating to DVCS: Why You should do it and how Atlassian's tools can help
- 3. DVCS: Making the Move? How Atlassian can help... Matthew Watson FishEye/Crucible Team Lead, Atlassian 2
- 4. Why DVCS? • Lots of people excited by it • Huge in Open Source • But what about Commercial in-house development? • What about the costs of migrating? 3
- 5. What’s Great about DVCS? • Work offline • Easier branching and merging • Github and Bitbucket • Do we really need this? 4
- 6. What’s really cool about DVCS! • What does ‘D’ in DVCS stand for? 5
- 7. What’s really cool about DVCS! • What does ‘D’ in DVCS stand for? • Distributed • Commit often, push when ready • Fast, peer-to-peer, no central server • Flexibility: Clones vs Branches 5
- 8. What’s really cool about DVCS? • What should the ‘D’ in DVCS stand for? 6
- 9. What’s really cool about DVCS? • What should the ‘D’ in DVCS stand for? • DAG = Directed Acyclic Graph Time • No loops • Each commit has 1 or more parents • Commits uniquely identified 6
- 10. SVN Commits Bob Mary Will r38 7
- 11. SVN Commits A.java Bob Mary Will r38 r39 7
- 12. SVN Commits A.java Bob B.java Mary Will r38 r39 r40 7
- 13. SVN Commits A.java Bob B.java Mary C.java Will r38 r39 r40 r41 7
- 14. SVN Commits Will svn commit svn update A.java r38 B.java r38 C.java r41 8
- 15. SVN Commits Will svn commit svn update A.java r38 r39 B.java r38 r40 C.java r41 r41 8
- 17. DAG Commits Bob 38:fb38fed187ab A.java 39:bb0760b60a8b 9
- 18. DAG Commits Bob 38:fb38fed187ab A.java 39:bb0760b60a8b Mary B.java 40:d0f08ba891a0 9
- 19. DAG Commits Bob 38:fb38fed187ab A.java 39:bb0760b60a8b Mary B.java 40:d0f08ba891a0 Will C.java 41:38ff647618b5 9
- 20. DAG Commits Bob 38:fb38fed187ab A.java 39:bb0760b60a8b Mary B.java 40:d0f08ba891a0 42:7d0e20243949 Will C.java 41:38ff647618b5 9
- 21. DAG Commits Bob 38:fb38fed187ab A.java 39:bb0760b60a8b Mary B.java 40:d0f08ba891a0 42:7d0e20243949 Will C.java 41:38ff647618b5 43:5fcdd3657717 9
- 22. The Power of the DAG • Deterministic • Annotate/blame works! • Easy and powerful merges - Don’t be scared of long running branches! • Easy and powerful branching 10
- 23. Traceability • In SVN/CVS etc merges hide what happened Time • In DVCS, the DAG lets you see exactly what changed 11
- 24. Flexibility • Single Integrator, Gatekeeper • Feature branches, git-flow • Clones • Automation • No central repository 12
- 25. Workflows, Workflows, Workflows • Which workflow to use? • “With Great Power there must also come - Great Responsibility!” - Spider Man? • Take your time! 13
- 26. Feature Branching • Branching and merging cheap and easy Time • All feature work done on branch • Can merge to any descendant 14
- 27. Feature Branching Workflow default Time 15
- 28. Feature Branching Workflow Create Feature Branch FE-143 FE-143 default Time 15
- 29. Feature Branching Workflow Squash Bugs! FE-143 default Time 15
- 30. Feature Branching Workflow FE-127 Complete FE-127 FE-143 default Time 15
- 31. Feature Branching Workflow Merge latest from default, build, test and FE-127 FE-143 default Time 15
- 32. Feature Branching Workflow Merge to default, close JIRA, set fix version FE-127 FE-143 default Time 15
- 33. Feature Branching Workflow FE-127 Stable code! FE-143 default Time 15
- 34. Cross Branch Dependencies • Can merge to any downstream branch • Easily merge fixes for releases into subsequent versions • Also works for feature branches • Our code is naturally becoming more stable 16
- 35. Migrating to DVCS • Which DVCS? • Small team - just go for it! • Large team - Don’t Fu$%! your devspeed! • Our goal - Zero downtime 17
- 36. Sync from SVN • Git SVN and HgSubversion • Incremental conversion • Remap Committers • mwatson = Matthew Watson <mwatson@atlassian.com> • Build Processes 18
- 37. Use Continuous Integration! • Vital part of dev cycle • Run same builds against old and new VCS • Continuous Validation 19
- 38. Use FishEye! • Sales Pitch • Commit Graph • See your commits in SVN and DVCS 20
- 39. Use Crucible! • Code reviews against DVCS Commits • Developers get used to the new way • New Commit ids • Committers map to Users 21
- 40. Make the Switch • Setup Clones and IDE’s before hand • Make SVN read-only • Go DVCS! 22
- 41. DVCS is Awesome! • More power = more opportunity to do things faster! • The DAG gives traceability, powerful branching and merging, speed • Migrating is easy! @mattw_watson #summit11 23
- 42. Questions • Our Blogs: http://blogs.atlassian.com/developer • Mercurial: http://mercurial.selenic.com/ • https://bitbucket.org/durin42/hgsubversion/overview/ • Git: http://git-scm.com • http://www.kernel.org/pub/software/scm/git/docs/git-svn.html • http://john.albin.net/git/convert-subversion-to-git • http://nvie.com/posts/a-successful-git-branching-model/ 24
Editor's Notes
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- &#x201C;you might be thinking&#x201D;\n
- Intro: \nAdvantages of DVCS (git & hg/mercurial) compared to Traditional VCS\nWhat we&#x2019;ve learned about DVCS\nOptions for migrating and our migration\nEnd up thinking migrating to DVCS is awesome idea\nDrop nuggets along the way\n?What VCS&#x2019;s using now?\n?Migrated? Thinking of Migrating?\n
- Momentum\n
- What do we know is good?\nWork Offline (local commits), easy to create new repo, faster\nEasier branching and merging &#x201C;apparently&#x201D;: Who branches in SVN?\nforks, pull request, OS stuff - new models\n
- Distributed:\npush when you want - commit often\ncreate local repos, push to others\nfast, fast history\ndefine clones?\nclones or branches, more flexibility - new workflows (more later)\nNothing compelling yet?\n
- * Important: This is what we discovered\n* SVN/CVS: Linear, concurrent changes\n* DAG: Commits built on parent commits - uniquely identified - new commits made by one author only - concurrent commits are merged\n* demonstrate\n
- * Linear\n* Overlap unintentionally\n
- * Linear\n* Overlap unintentionally\n
- * Linear\n* Overlap unintentionally\n
- Unintended state\nCI was invented to deal with this\n
- Contrast to in SVN, changes made at same time, but appear as logical progression\nDVCS: Commits build on a known state\n
- Contrast to in SVN, changes made at same time, but appear as logical progression\nDVCS: Commits build on a known state\n
- Contrast to in SVN, changes made at same time, but appear as logical progression\nDVCS: Commits build on a known state\n
- Contrast to in SVN, changes made at same time, but appear as logical progression\nDVCS: Commits build on a known state\n
- Contrast to in SVN, changes made at same time, but appear as logical progression\nDVCS: Commits build on a known state\n
- Lots of merges: yes, but deliberate, tracked, only merge a change once! \nMerging: very powerful - track copies/moves - long running refactoring\nCan &#x201C;branch&#x201D; at any point - each concurrent commit IS a branch - merge to any descendant\n\n
- Graph Queries, 20% JIRA integration\nPause\n
- distributed nature + DAG = lots of options\nNo-one tells you which one is best!\n\n
- Stay with what you know - mimic SVN workflow\n get used to whats possible - devs will experiement\n adapt slowly\n\n
- Us: Started using branching -> release & feature branching (all work on releases like this!)\nBranch from earliest common point you might want to merge to\n\n
- Review->Build (BB3.1, 20% project)->complete merge/fixVersion & close JIRA\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Review->Build (BB3.1, 20% project)\nFeature branch balance - size - life time - naturally evolve - big work - integrate from stable\n
- Works for feature branches too\nDid this on SVN, but as mentioned already - merges only merge new stuff & Traceability\nFeature Branches: can merge to others before integrated to stable\n\n
- Options: All in one or gradual\n
- Git SVN and HgSubversion allow you to work on a SVN repository using git/hg as a client - also used for converting\nCan pull at will - by setting up a cron job, can continuously pull changes into git/hg - then push them to your hosting service (github/bitbucket)\nCan also remap committer names, exclude file paths, more info on our blogs.\nMigrate any build/release/test processes that rely on the VCS\n\n
- \n
- RSS feeds of changes, activity streams, URL to changes, Search, Commit Graph\n Get Used to Commit hashes etc.\n
- Start doing code reviews against synced DVCS\nDifferences\nEngage developers\n
- we very happy, devs sceptical, but now all see benefits\n
- Convinced you there is more to DVCS than you might have thought\n
- * Slides will be available\n