Imports of package source

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
github.com/moby/buildkit/cache
github.com/moby/buildkit/session
github.com/moby/buildkit/solver
github.com/moby/buildkit/solver/llbsolver/provenance
github.com/moby/buildkit/solver/pb
github.com/pkg/errorsPackage errors provides simple error handling primitives.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.
syncPackage sync provides basic synchronization primitives such as mutual exclusion locks.