Ensuring product quality and engineering productivity in an Agile environment with numerous concurrent branches can be challenging. In this presentation, Yi Zhang of EMC will share his team's branch management lessons and discuss the merge tool they've developed based on P4PERL. Hear how EMC leverages this tool to try and achieve great code quality and high engineering productivity at the same time.

1. Branch Management and
Atomic Merge in a Continuous
Integration Environment
Yi Zhang and Ray Chang
EMC Corporation
© 2011

2. AGENDA
THE ISSUES
• What’s Wrong?
THE SOLUTIONS
• The New Branch and Defect Model
• The Atomic Merge Tool – Logical Flow
• Integration with Defect-Tracking
CONCLUSIONS
• Achievements
• Remaining Issues
Q@A

3. THE ISSUES – What’s wrong with this version tree?

4. THE ISSUES
• Anarchic Branching
• Merge-phobia, unable to merge
• Tremendous loss in productivity
Stubborn and egregiously harmful institutional habits
formed over the years. Migrating to continuous
integration exacerbated the issues.

5. THE SOLUTIONS – New Branch Model
• The branch model and naming conventions

6. THE SOLUTIONS – New Defect Model
• The defect model and Perforce directory structure

7. THE SOLUTIONS – The merge tool
• No significant change in merge habit
• Improvement limited on the Defect-tracking side
• Divergent branches still an issue
Based on “p4 integrate” of P4PERL, implemented an
auto-merge tool to merge daily atomically among
branches.

8. THE SOLUTIONS – The atomic merge tool
• Logical flow chart of the merge tool

9. THE SOLUTIONS – The atomic merge tool
A few assumptions:
• Changelist restricted within a project branch
• Merge occurred among the tips
• Exclusions override the atomic rule

10. THE SOLUTIONS – Integration with defect-tracking

11. THE SOLUTIONS – The atomic merge tool
A few more points:
• Web interface for ad hoc merge requests
• Integration with the continuous integration tool
• Running quality tool as a step of post-merge verification

12. CONCLUSIONS
Achievements:
• A set of branching and merging policies are established
and implemented
• Atomic merge tool is successfully adopted by many
teams and sites
• Over 95% of automatic merge rate, significantly
reduced manual work and enhanced productivity

13. CONCLUSIONS
Remaining issues:
• How to prevent merge-up?
• “p4 integrate” doesn’t always recognize duplicated
check-ins.
• Significant number of project teams not on board yet.

14. QUESTIONS @ ANSWERS