Lessons Learned: Transforming from ClearCase to Git

Tamir Gefen

@almtoolboxalmtoolbox.com

Why Switching Tools? The Situation

The Situation1. 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

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Why Switch Tools?

Why Switch Tools?

1. Costs: licensing and maintenance

2. Ease of use for end-users

3. Consolidate the organization into one tool

AgendaChallengesChallenges

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

Different Tools?

Different Tools?

Not so different…

Similarities:

Project structure

Branching

Users and permissions

Differences:

Working copies

Work items

Are Git and ClearCase different tools?

The Transition

The Transition (Planning)

1. Migration strategy

2. New flow

3. Training

4. Limited timeframe

The Transition

main (master) R1.0

R1.1

R2.0

R2.1

Migration strategy

Lesson LearnedResults

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

Lessons Learned

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)

Tips

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!

tgefen@almtoolbox.com

Thank You!