Upstream (software development)

In the context of software development, "upstream" refers to the source or origin of a software component, typically a library, patch, or the main project itself. It represents the direction of code flow from the original developer or maintainer towards derivative works or distributions.

More specifically, "upstream" can refer to:

• The Original Project: The primary, canonical version of a software project. If you're using a library from GitHub, the GitHub repository owned by the library's creator is the upstream source.

• The Source of a Patch: When submitting a bug fix or feature enhancement, the "upstream" is the project or repository where you are proposing to contribute the change.

• The Maintainers or Developers: Those responsible for the upstream project, who decide whether to accept, modify, or reject contributions.

The relationship between "upstream" and derived projects (also known as "downstream") is crucial for managing software dependencies, bug fixes, and feature additions. When a bug is fixed upstream, it ideally propagates downstream through updates or patching processes. Downstream projects are often encouraged to contribute their changes back upstream, allowing the original project to benefit from the improvements and avoiding code duplication. This process also assists in maintaining a central, reliable source of code.

Contributing changes "upstream" involves submitting a patch, pull request, or other form of contribution to the upstream project. This allows the maintainers to review and potentially integrate the changes into the official codebase.

The term "upstream" is also used as a verb. For example, "We should upstream this patch" means "We should contribute this patch to the original project."