I recently came across an MSDN article about branching and merging and SCM: Branching and Merging Primer – Chris Birmele.
In the article they say 'big bang merge' is a merging antipattern:
Big Bang Merge — deferring branch merging to the end of the
development effort and attempting to merge all branches
simultaneously.
I realized that this is very similar to what my company is doing with all of the development branches that are produced.
I work at a very small company with one person acting as the final review + trunk merge authority. We have 5 developers (including me), each of us will be assigned a separate task/bug/project and we will each branch off the current trunk (subversion) and then perform the development work in our branch, test the results, write documentation if necessary, perform a peer review and feedback loop with the other developers, and then submit the branch for review + merge on our project management software.
My boss, the sole authority on the trunk repository, will actually defer all of the reviews of branches until a single point in time where he will perform reviews on as much as he can, some branches will be thrown back for enhancements/fixes, some branches will merge right into trunk, some branches will be thrown back because of conflicts, etc.
It's not uncommon for us to have 10-20 active branches sitting in the final review queue to be merged into trunk.
We also frequently have to resolve conflicts in the final review and merge stage because two branches were created off the same trunk but modified the same piece of code. Usually we avoid this by just rebranching off trunk and re-applying our changes and resolving the conflicts then submitting the new branch for review (poor mans rebase).
Some direct questions I have are:
- Are we exhibiting the very anti-pattern that was described as the 'big bang merge'?
- Are some of the problems we're seeing a result of this merge process?
- How can we improve this merge process without increasing the bottleneck on my boss?
Edit: I doubt my boss will loosen his grip on the trunk repository, or allow other devs to merge to trunk. Not sure what his reasons for that are but I don't really plan on bringing the topic up because it's been brought up before and shot down rather quickly. I think they just don't trust us, which doesn't make sense because everything is tracked anyway.
Any other insight into this situation would be appreciated.
Best Answer
Some suggestions:
There is nothing wrong in having a lot of feature or bugfix branches as long as the changes done in each branch are small enough you can still handle the resulting merge conflicts in an effective manner. That should be your criterion if your way of working is ok, not some MSDN article.
Whenever a branch is merged into trunk, the trunk should be merged into all open development branches ASAP. This would allow all people in the team to resolve merge conflicts in parallel in their own branch and so take some burden from the gatekeeper of the trunk.
This would work way better if the gatekeeper would not wait until 10 branches are "ready for merging into trunk" - resolving merge conflicts from the last trunk integrations always needs some time for the team, so it is probably better to work in interwoven time intervals - one integration by the gatekeeper, one re-merge by the team, next integration by the gatekeeper, next re-merge by the team, and so on.
To keep branches small, it might help to split larger features into several smaller tasks and develop each of those tasks in a branch of its own. If the feature is not production ready until all subtasks are implemented, hide it from production behind a feature toggle until all subtasks are completed.
Sooner or later you will encounter refactoring tasks which affect many files in the code base - these have a high risk of causing a lot merge conflicts with many branches. Those can be handled best by communicating them clearly in the team, and make sure to handle them exactly as I wrote above: by integrating them first into all dev branches before reintegration, and by splitting them up into smaller sub-refactorings.
For your current team size, having a single gatekeeper may still work. But if your team will grow in size, there is no way around having a second gatekeeper (or more). Note I am not suggesting to allow everyone to merge into trunk, but that does not mean only your boss is capable of doing this. There are probably one or two senior devs who could be candidates for doing the gatekeeper's job, too. And even for your current team's size, a second gatekeeper could make it easier for your team to integrate to the trunk more often and earlier, or when your boss is not available.