gotools/go/buildutil/overlay.go

// OverlayContext overlays a build.Context with additional files from
// a map. Files in the map take precedence over other files.
//
// In addition to plain string comparison, two file names are
// considered equal if their base names match and their directory
// components point at the same directory on the file system. That is,
// symbolic links are followed for directories, but not files.
//
// A common use case for OverlayContext is to allow editors to pass in
// a set of unsaved, modified files.
//
// Currently, only the Context.OpenFile function will respect the
// overlay. This may change in the future.
func OverlayContext(orig *build.Context, overlay map[string][]byte) *build.Context { … }

// ParseOverlayArchive parses an archive containing Go files and their
// contents. The result is intended to be used with OverlayContext.
//
// # Archive format
//
// The archive consists of a series of files. Each file consists of a
// name, a decimal file size and the file contents, separated by
// newlines. No newline follows after the file contents.
func ParseOverlayArchive(archive io.Reader) (map[string][]byte, error) { … }