sbt 1.4.0 / Zinc 1.4.0 virtualizes the file paths tracked during incremental compilation, and uses content hash for change detection. With these combination, we can realize repeatable build, also known as build as function.
This enables experimental remote caching (cached compilation) feature. The idea is for a team of developers and/or a continuous integration (CI) system to share build outputs. If the build is repeatable, the output from one machine can be reused by another machine, which can make the build significantly faster.
ThisBuild / pushRemoteCacheTo := Some(MavenCache("local-cache", file("/tmp/remote-cache")))
Then from machine 1, call pushRemoteCache. This will publish the *.class and Zinc Analysis artifacts to the location. Next, from machine 2, call pullRemoteCache.
As of sbt 1.4.0, we’re reusing the Maven publishing and resolution mechanism to exchange the cached build outputs. This is likely to easy to get started using existing infrastructure such as Bintray.
In the future, we might consider simpler cache server like plain HTTP server that uses PUT and GET. This would require someone to host an HTTP server somewhere, but provisioning them might become simpler.
To abstract machine-specific paths such as your working directory and Coursier cache directory, sbt keeps a map of root paths in ThisBuild / rootPaths. If your build adds special paths for your source or output directory, add them to ThisBuild / rootPaths.
If you need to guarantee that ThisBuild / rootPaths contains all necessary paths you can set ThisBuild / allowMachinePath to false.
As of sbt 1.4.2, remoteCacheId uses hash of content hashes for input sources.
