7 May 2020
A feature branch is a source code branching pattern where a developer opens a branch when she starts working on a new feature. She does all the work on the feature on this branch and integrates the changes with the rest of the team when the feature is done.
During the work, she may merge in changes confirmed by the rest of the team into her branch, in order to reduce her integration once the feature is complete, but she doesn't put her changes into the common codebase until that point. This has the consequence that two people, working on different feature branches, do not integrate their work until the second one merges their work into the common codebase.
Feature branches are a popular technique, particularly well-suited to open-source development. They allow all the work done on a feature to kept away from a teams common codebase until completion, which allows all the risk involved in a merge to be deferred until that point. However this isolation does prevent early detection of problems. More seriously, it also discourages refactoring - and a lack of refactoring often leads to serious deterioration in the health of a codebase.
The consequences of using feature branch depend greatly on how long it takes to complete features. A team that typically completes features in a day or two are able to integrate frequently enough to avoid the problems of delayed integration. Teams that take weeks, or months, to complete a feature will run into more of these difficulties.
For more details on feature branching, see my long form article on Patterns for Managing Source Code Branches. This sets the feature branching pattern into the broader picture of using branching in software development, breaks down the workflow of working on a feature branch, discusses the trade-offs involved with the frequency of integration, and explores the alternative of Continuous Integration.
I published my original post on this URL on 3 Sep 2009. When I published Patterns for Managing Source Code Branches I cut this page down to a short summary.