Scala .gitignore template

target is the output directory the build tool writes into, and in a multi project build there is one per subproject plus one at the root. It holds compiled classes, packaged artefacts, generated sources and the incremental compilation analysis. The rule is unanchored precisely so it catches all of them without you listing every module.

.bsp is the build server protocol directory. It contains connection files telling an editor how to start the build server for this project, including the absolute path to the launcher on the machine that generated them. Two developers with different installations will produce different files, so committing one guarantees a conflict.

.metals and .bloop are the language server and compile server working directories. Metals keeps its symbol index, semantic database and logs there; Bloop keeps generated build configuration in JSON, again full of absolute classpath entries. Both are rebuilt from the build definition when the editor next opens the project.

project/metals.sbt is a plugin file the language server writes into your build to enable its own integration. It is a tool detail rather than part of the project definition, and a teammate using a different editor has no use for it. project/project is the meta build's own output directory, one level up the recursive build definition that the build tool uses to compile the build itself.

.scala-build is the working directory used by the single file scripting tool, holding compiled output and resolved dependencies for scripts that are not part of a full build definition. Like the rest of the list it is derived state with a short lifetime.