Rename LazyContext to LazySource.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

builder/dockerfile/copy.go

@@ -155,7 +155,7 @@ func (o *copier) calcCopyInfo(origPath string, allowWildcards bool) ([]copyInfo,
 		var err error
 		o.source, err = imageSource.Source()
 		if err != nil {
-			return nil, errors.Wrapf(err, "failed to copy")
+			return nil, errors.Wrapf(err, "failed to copy from %s", imageSource.ImageID())
 		}
 	}
 
@@ -359,7 +359,7 @@ func downloadSource(output io.Writer, stdout io.Writer, srcURL string) (remote b
 		return
 	}
 
-	lc, err := remotecontext.NewLazyContext(tmpDir)
+	lc, err := remotecontext.NewLazySource(tmpDir)
 	return lc, filename, err
 }
 
@@ -383,7 +383,7 @@ func copyFile(dest copyInfo, source copyInfo, options copyFileOptions) error {
 
 	src, err := os.Stat(srcPath)
 	if err != nil {
-		return err // TODO: errors.Wrapf
+		return errors.Wrapf(err, "source path not found")
 	}
 	if src.IsDir() {
 		if err := archiver.CopyWithTar(srcPath, destPath); err != nil {

builder/dockerfile/imagecontext.go

@@ -156,7 +156,7 @@ func (im *imageMount) Source() (builder.Source, error) {
 		if err != nil {
 			return nil, errors.Wrapf(err, "failed to mount %s", im.image.ImageID())
 		}
-		source, err := remotecontext.NewLazyContext(mountPath)
+		source, err := remotecontext.NewLazySource(mountPath)
 		if err != nil {
 			return nil, errors.Wrapf(err, "failed to create lazycontext for %s", mountPath)
 		}

builder/dockerfile/internals.go

@@ -100,7 +100,7 @@ func (b *Builder) performCopy(state *dispatchState, inst copyInstruction) error
 	}
 	destSource, err := imageMount.Source()
 	if err != nil {
-		return err
+		return errors.Wrapf(err, "failed to mount copy source")
 	}
 
 	destInfo := newCopyInfoFromSource(destSource, dest, "")

builder/remotecontext/detect.go

@@ -81,7 +81,7 @@ func withDockerfileFromContext(c modifiableContext, dockerfilePath string) (buil
 }
 
 func newGitRemote(gitURL string, dockerfilePath string) (builder.Source, *parser.Result, error) {
-	c, err := MakeGitContext(gitURL) // TODO: change this to NewLazyContext
+	c, err := MakeGitContext(gitURL) // TODO: change this to NewLazySource
 	if err != nil {
 		return nil, nil, err
 	}

builder/remotecontext/lazycontext.go

@@ -12,30 +12,30 @@ import (
 	"github.com/pkg/errors"
 )
 
-// NewLazyContext creates a new LazyContext. LazyContext defines a hashed build
+// NewLazySource creates a new LazyContext. LazyContext defines a hashed build
 // context based on a root directory. Individual files are hashed first time
 // they are asked. It is not safe to call methods of LazyContext concurrently.
-func NewLazyContext(root string) (builder.Source, error) {
-	return &lazyContext{
+func NewLazySource(root string) (builder.Source, error) {
+	return &lazySource{
 		root: root,
 		sums: make(map[string]string),
 	}, nil
 }
 
-type lazyContext struct {
+type lazySource struct {
 	root string
 	sums map[string]string
 }
 
-func (c *lazyContext) Root() string {
+func (c *lazySource) Root() string {
 	return c.root
 }
 
-func (c *lazyContext) Close() error {
+func (c *lazySource) Close() error {
 	return nil
 }
 
-func (c *lazyContext) Hash(path string) (string, error) {
+func (c *lazySource) Hash(path string) (string, error) {
 	cleanPath, fullPath, err := normalize(path, c.root)
 	if err != nil {
 		return "", err
@@ -62,7 +62,7 @@ func (c *lazyContext) Hash(path string) (string, error) {
 	return sum, nil
 }
 
-func (c *lazyContext) prepareHash(relPath string, fi os.FileInfo) (string, error) {
+func (c *lazySource) prepareHash(relPath string, fi os.FileInfo) (string, error) {
 	p := filepath.Join(c.root, relPath)
 	h, err := NewFileHash(p, relPath, fi)
 	if err != nil {