project in file(".")
project in file(".")in SBT "short" for
Yes, it is (it's actually not "short", it's called infix notation).
in method does is set the base directory for the project you're creating with a bunch of configurations and definitions:
/** Sets the base directory for this project.*/ def in(dir: File): Project = copy(base = dir)
And finally it ends up creating a new project definition for you (inside the
new ProjectDef[ProjectReference]( id, base, aggregate, dependencies, delegates, settings, configurations, auto, plugins, autoPlugins) with Project
And on top of that, you apply a bunch of settings and dependencies.