About

What is hammerkit?

Hammerkit is a build tool intended to build software projects in containers locally and in CI. The advantages of containerized builds are:

• the build tools come from the container image, so they are the same across all machines.
• the build process is isolated since every file in the container has to be declared as a source or an output. Therefore, side effects can be reduced.

For a fuller pitch — including how it compares to Make, npm scripts, Taskfile and Earthly — see Why hammerkit.

There are a lot of containerized CI systems that allow writing containerized builds today, but they have shortcomings that hammerkit tries to address:

• they are often not usable during development on your local machine, so you either have to maintain two build scripts or wrap one of them in the other.
• they mount the entire repository into the container, so uncontrolled side effects can reduce reliability.
• some of them do not allow switching images between build steps, requiring you to maintain one large build image that contains every tool needed to build the software.

Additionally, hammerkit tries to reduce the complexity of build caching in CI systems. Usually you define a directory that is restored before and cached after the CI build. That's fine for smaller projects with only a few directories to cache. The bigger the project gets, the more effort it takes to keep all of those directories up to date.

Hammerkit, on the other hand, knows the source and output files of each build step and can therefore compact the build results into a single directory, which is easy to cache — or share them through a remote cache. Once restored, hammerkit detects what has changed since the last run and only builds the changes.

Where to go next?

Check out the docs on hammerkit.dev for more info about how hammerkit can be used.