ContainingDirectory finds the parent directory of child containing an entry named by tombstones.

FindProjectRoot finds the root directory of the project containing path, which can be a file or a directory.

HasSubdir calls ctxt.HasSubdir (if not nil) or else uses the local file system to answer the question.

HasSubdirFunc returns a function that can be used for build.Context.HasSubdir field and is significantly faster than the default implementation.

ScopedContext returns a build.Context with a ReadDir that is scoped to the directories listed by pkgdirs and the GOROOT.

DefaultProjectTombstones are the files used by FindProjectRoot to determine the root of a project.