Currently, userConfig is only read once at startup and then never changes. Later
in this branch, we will add the possibility to reload the user config; this can
happen either when switching repositories, or when the user has edited the
config file. In both cases, reloading happens on the main thread, but the user
config could be accessed concurrently from background threads, so we need to
make this safe.
Afero is a package that lets you mock out a filesystem with an in-memory filesystem.
It allows us to easily create the files required for a given test without worrying about
a cleanup step or different tests tripping on eachother when run in parallel.
Later on I'll standardise on using afero over the vanilla os package
