A package that contains checks that npm runs during the installation.
.checkEngine(target, npmVer, nodeVer, force, strict, cb)
Check if node/npm version is supported by the package.
.checkPlatform(target, force, cb)
Check if OS/Arch is supported by the package.
.checkCycle(target, ancestors, cb)
Check for cyclic dependencies.
Check if a folder is a .git folder.