This is a short case study on moving to Git from IBM Rational ClearCase (that was delivered during Git Merge 2017 conference). Attendees will learn about challenges we faced and how we resolved them, plus some technical tips and insights.

1. Lessons Learned: Transforming
from ClearCase to Git
Tamir Gefen
@almtoolboxalmtoolbox.com

2. Why Switching Tools?The Situation

3. The Situation
1. 100 developers (end-users); 5 groups
2. Working with Base ClearCase ; hundreds of branches
3. Users want to work from home in a convenient way
4. Users want to move to modern processes

4. Why Switch Tools?

5. Why Switch Tools?
1. Costs: licensing and maintenance
2. Ease of use for end-users
3. Consolidate the organization into one tool

6. Agenda
ChallengesChallenges

7. The Challenges
1. Different tools?
2. Train 100 developers in how to use a new system
3. New development concept. Set a new flow?
4. Integrated with IDEs?
5. How to move history? Should we take the whole history?
6. Train administrators in how to operate git
7. Limited (and short) timeframe

8. Different Tools?

9. Different Tools?
Not so different…
Similarities:
 Project structure
 Branching
 Users and permissions
Differences:
 Working copies
 Work items
Are Git and ClearCase different tools?

10. The Transition

11. The Transition (Planning)
1. Migration strategy
2. New flow
3. Training
4. Limited timeframe

12. The Transition
main (master)
R1.0
R1.1
R2.0
R2.1
Migration strategy

13. Lesson LearnedResults

14. Results
1. Licensing costs: 0
2. New flow
3. Shorter learning curve (than before)
4. New options for integrating with modern tools, including issue-
tracking; CI and more

15. Lessons Learned

16. Lessons Learned
1. You can move active baselines / labels only
2. Move each SW group separately
3. Allocate 1-2 days to accommodate developers (after migration)
4. The transition is an opportunity to improve SW processes
5. Transition should be planned by a person who knows BOTH
ClearCase and Git
6. Define SUCCESS criteria (acceptance tests)

17. Tips

18. Tips
1. Build a table translating ClearCase-ish to Git-ish
(e.g.: check-in -> commit, label -> tag(
2. Print the new flow (as a diagram) and share it with the end-users
3. Use strong and reliable infrastructures
4. Beware of ClearCase “evil twins” and hard links!

19. tgefen@almtoolbox.com
Thank You!