On the Evilness of Feature Branching - A Tale of Two Teams


On the experience of working with two totally different teams: one novice practising trunk-based development, the other very experienced being used by GitFlow.


In 2012, I started a technical coaching mission to upscale the software engineering skills of a rather novice team. Novice from an engineering perspective, not so much from a working-experience perspective. They had working experience ranging from 5 to 20 years. Sometimes, people do not have the luxury to attend the right conferences. Or to work with people that would show them different ways of working.

Luckily, we were the two of us to coach the team. Pair-coaching is tremendously reassuring. Especially when you have to introduce plenty of changes with people having many years of working experience.

At the start, we came upon a situation we were not expecting to still discover in 2012. No one in the team, except for one person, was using any version control system. Code was shared amongst team members using … shared drives. Deployments also happened from … shared drives.

It seems this no-version control anti-pattern is applied more often than expected as I discovered again in 2018 and 2020.

Historically I meet 1 team a year on average who aren’t using version/source code control. Common reasons:

  • very immature team
  • SQL
  • PickOS derivative or ERM/CRM system

Last category may even lack tooling

– Allan Kelly @allankellynet, Nov 8, 2020

Obviously, as a first action, we introduced version control. As the team was a novice in using version control systems, I thought Git would be a bridge too far. Too many concepts to learn. Therefore I suggested SubVersion. It is pretty easy to use. You only have three concepts to grasp:

  • You check out the code,
  • you modify it,
  • and you check it back in.
  • And you are done. Fairly simple, isn’t it?

Because by all accounts branching was reasonably painful with SubVersion - less troublesome than with CVS but still more demanding than with Git - I also suggested using no branches at all. Everyone in the team was going to commit directly into trunk. Frankly, at the time, I did not understand much about branching strategies. It all seemed too complicated to me. I had hard times trying to fit the workflow in my head.

That worked pretty well. Because … there was a second thing we introduced, right from the start, the practice of Continuous Integration and team-commitment that any change had to be covered by automated tests, preferably unit tests.

Continuous Integration later evolved towards Continuous Delivery.

At the time, I did not realise this was a valid branching strategy. And that it actually had a name. It is only years later I discovered it was named Trunk-Based Development.

Was trunk never broken? Admittedly, yes, it happened. More often than good. Remember, this was a novice team. But that was not really a problem. Because Continuous Integration was in place, allowing us to discover any breaking change early, and to fix it immediately while it was still small and easy to fix.

When the team gained maturity, we thought it was time to migrate to Git. The reasons for that decision were twofold:

  • there is more tooling available to manage Git repos;
  • and we wanted to adopt the Pull-Request model for code reviews and so branch creation had to be effortless without friction.

But … what works for the open-source community, where a core team maintains a system and accepts contributions from the outside, does not necessarily work very well for a co-located team in a corporate environment.

Like all powerful tools, there are many ways you can use them [DVCS], and not all of them are good.

– Jez Humble, On DVCS, continuous integration, and feature branches

The fact that proponents of Distributed Version Control Systems (DVCS) rely on feature branching to sell DVCSs together with all the tooling that exists around DVCSs makes everyone blind to the problems created by the use of feature branching.

With the team, we have hit these problems violently. We tried to find solutions by introducing ever more entangled processes and ever more complicated technology. But it never really solved the underlying problem except for adding a significant amount of complexity. In the end, we sat together to discuss the matter and decided to let go of the use of feature branches. We went back to what worked for us, i.e. trunk-based development. We never looked back.

In January 2021, 8 years later, I was invited by the team’s organisation to present Feature Branching is Evil as part of training. During the question and answer, I discovered the team is still practising trunk-based development. They can still not imagine a different way of working. For them, it is the most natural thing to do.

After this experience, somewhere in 2016, I started a new mission in a totally different organisation. Very agile, working with highly skilled engineers where everyone was working in pairs most of the time. But … they decided as an organisation to use GitFlow. When arriving, I discovered branches were living from 5 days to somewhere 30 days. People had to rebase mainline frequently into their branches, causing lots of rework and spending much non-valuable time on fixing what got broken.

With the experience I gained working with that novice team, I suggested running an experiment with trunk-based development. At the time, a new project was going to start. Only two people would work on that project. You would already wonder in the first place, why bother to use GitFlow on a 2-persons project. That experiment was not going to be very risky, is it?

Convincing people about the immeasurable rewards of Trunk Based Development is not an overnight task.

– Iqbal Ahmed @propattern, Nov 24, 2016

Whenever I suggest trunk-based development, especially in front of experienced, skilled engineers, I always get that same reaction: People stare at me like I am an idiot. “Are you insane? Branching is a commonly accepted practice in the industry. Are you suggesting to have the whole team committing immediately into mainline? It will be a mess. We will have merge conflicts all over the place!”.

The idea that developers should work in small batches off master or trunk rather than on long-lived feature branches is still one of the most controversial ideas in the Agile canon, despite the fact it is the norm in high-performing organizations such as Google.

– 2016 State of DevOps Report

Although trunk-based development is implied by Continuous Integration;

Although trunk-based development has been reported since 2015 by the State of DevOps report to predict high software delivery performance;

Although trunk-based development is practised by organisations like Facebook, Microsoft, Netflix and Google at an immense large scale (in 2016 we were speaking about 25.000 developers working from one trunk with 16.000 changes per day);

Trunk-based development is still one of the most controversial practices in the IT industry.

In the end, I failed miserably in trying to get that organisation to just run a small experiment with trunk-based development. I was not able to bring over the possible benefits of trunk-based development. I lacked the correct arguments as I only had that one experience with that one novice team. Though I have used quite some branching strategies in my past career, I never really paid attention to the problems they introduce.

That mission was an opportunity to observe what happens when a team adopts a branching strategy like GitFlow, which resulted in my seminal presentation Feature Branching is Evil.

In closing, from the narrow set of data I have, we can conclude that you do not have to be a rock-star team to practice trunk-based development. Novice teams can do this, as well as experienced teams are not able to. It all comes down to having the right mindset. A can-do mindset. A whatever-happens-this-will-work mindset. And also knowing what practices to apply to facilitate this. I will come back to this in a future article.

Though I have a limited set of data, others having enough data as The State of DevOps Report and the book Accelerate have equally confirmed trunk-based development together with Continuous Integration is a predictor for Continuous Delivery, which in turn together with Lean Product Management and a Generative organisational culture predicts a high performing organisation.

Acknowledgment

Steve Smith for reviewing this series.

The Series

The On the Evilness of Feature Branching series:

  1. A Tale of Two Teams
  2. Why Do Teams Use Feature Branches?
  3. Why Are Feature Branches a Problem?
  4. How Can We Avoid Feature Branching Problems?
  5. Questions I Regularly Get Asked about Trunk-Based Development
  6. What Are The Benefits of Trunk-Based Development?
  7. Where is the Evilness of Feature Branching?