How do you maintain development code and production code?

We use:

• development branch exclusively

until the project nears completion, or we are creating a milestone version (eg. product demo, presentation version), then we (regularly) branch off our current development branch into the:

• release branch

No new features go into the release branch. Only important bugs are fixed in the release branch, and the code to fix these bugs is reintegrated into the development branch.

The two-part process with a development and a stable (release) branch makes life a lot easier for us, and i don't believe we could improve any part of it by introducing more branches. Each branch also has it's own build process, meaning every couple minutes a new build process is spawned and so after a code checkin we have a new executable of all build versions and branches within about half an hour.

Occassionally we also have branches for a single developer working on a new and unproved technology, or creating a proof of concept. But generally it's only done if the changes affects many parts of the codebase. This happens in average every 3-4 months and such a branch is usually reintegrated (or scrapped) within a month or two.

Generally i don't like the idea of every developer working in his own branch, because you "skip go and move directly to integration hell". I would strongly advise against it. If you have a common codebase, you should all work in it together. This makes developers more wary about their checkins, and with experience every coder knows which changes are potentially breaking the build and so testing is more rigorous in such cases.

On the check-in early question:

If you require only PERFECT CODE to be checked in, then actually nothing should get checked in. No code is perfect, and for the QA to verify and test it, it needs to be in the development branch so a new executable can be built.

For us that means once a feature is complete and tested by the developer it is checked in. It may even be checked in if there are known (non-fatal) bugs, but in that case the people who would be affected by the bug are usually informed. Incomplete and work-in-progress code can also be checked in but only if it doesn't cause any obvious negative effects, like crashes or breaking existing functionality.

Every now and then an unavoidable combined code & data checkin will make the program unusable until the new code has been built. The very least we do is to add a "WAIT FOR BUILD" in the check-in comment and/or send out an e-mail.

Update 2019:

These days, the question would be seen in a context using Git, and 10 years of using that distributed development workflow (collaborating mainly through GitHub) shows the general best practices:

• master is the branch ready to be deployed into production at any time: the next release, with a selected set of feature branches merged in master.
• dev (or integration branch, or 'next') is the one where the feature branch selected for the next release are tested together
• maintenance (or hot-fix) branch is the one for the current release evolution/bug fixes, with possible merges back to dev and or master

That kind of workflow (where you don't merge dev to master, but where you merge only feature branch to dev, then if selected, to master, in order to be able to drop easily feature branches not ready for the next release) is implemented in the Git repo itself, with the gitworkflow (one word, illustrated here).
See more at rocketraman/gitworkflow. The history of doing this vs Trunk-Based-Development is noted in the comments and discussions of this article by Adam Dymitruk.

^{(source: Gitworkflow: A Task-Oriented Primer)}

Note: in that distributed workflow, you can commit whenever you want and push to a personal branch some WIP (Work In Progress) without issue: you will be able to reorganize (git rebase) your commits before making them part of a feature branch.

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Original answer (Oct. 2008, 10+ years ago)

It all depends of the sequential nature of your release management

First, is everything in your trunk really for the next release? You might find out that some of the currently developed functions are:

• too complicated and still need to be refined
• not ready in time
• interesting but not for this next release

In this case, trunk should contain any current development efforts, but a release branch defined early before the next release can serve as consolidation branch in which only the appropriate code (validated for the next release) is merged, then fixed during the homologation phase, and finally frozen as it goes into production.

When it comes to production code, you also need to manage your patch branches, while keeping in mind that:

• the first set of patches might actually begin before to first release into production (meaning you know you will go into production with some bugs you can not fix in time, but you can initiate work for those bugs in a separate branch)
• the other patch branches will have the luxury to start from a well-defined production label

When it comes to dev branch, you can have one trunk, unless you have other development efforts you need to make in parallel like:

• massive refactoring
• testing of a new technical library which might change the way you calls things in other classes
• beginning of a new release cycle where important architectural changes need to be incorporated.

Now, if your development-release cycle is very sequential, you can just go as the other answers suggest: one trunk and several release branches. That works for small projects where all the development is sure to go into the next release, and can just be frozen and serve as a starting point for release branch, where patches can take place. That is the nominal process, but as soon as you have a more complex project... it is not enough anymore.

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To answer Ville M.'s comment:

• keep in mind that dev branch does not mean 'one branch per developer' (which would trigger 'merge madness', in that each developer would have to merge the work of other to see/get their work), but one dev branch per development effort.
• When those efforts need to be merged back into trunk (or any other "main" or release branch you define), this is the work of the developer, not - I repeat, NOT - the SC Manager (who would not know how to solve any conflicting merge). The project leader may supervise the merge, meaning make sure it starts/finish on time.
• whoever you choose for actually doing the merge, the most important is:
  • to have unit tests and/or assembly environment in which you can deploy/test the result of the merge.
  • to have defined a tag before the beginning of the merge in order to be able to get back to previous state if said merge proves itself too complex or rather long to resolve.