1 files changed, 56 insertions, 1 deletions
diff --git a/pkg/copy/fileinfo.go b/pkg/copy/fileinfo.go
index 08b4eb377..50b0ca9a1 100644
--- a/pkg/copy/fileinfo.go
+++ b/pkg/copy/fileinfo.go
@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"os"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -15,6 +16,10 @@ import (
 // base64 encoded JSON payload of stating a path in a container.
 const XDockerContainerPathStatHeader = "X-Docker-Container-Path-Stat"
 
+// ENOENT mimics the stdlib's ENONENT and can be used to implement custom logic
+// while preserving the user-visible error message.
+var ENOENT = errors.New("No such file or directory")
+
 // FileInfo describes a file or directory and is returned by
 // (*CopyItem).Stat().
 type FileInfo struct {
@@ -23,7 +28,6 @@ type FileInfo struct {
 	Mode       os.FileMode `json:"mode"`
 	ModTime    time.Time   `json:"mtime"`
 	IsDir      bool        `json:"isDir"`
-	IsStream   bool        `json:"isStream"`
 	LinkTarget string      `json:"linkTarget"`
 }
 
@@ -54,3 +58,54 @@ func ExtractFileInfoFromHeader(header *http.Header) (*FileInfo, error) {
 
 	return &info, nil
 }
+
+// ResolveHostPath resolves the specified, possibly relative, path on the host.
+func ResolveHostPath(path string) (*FileInfo, error) {
+	resolvedHostPath, err := filepath.Abs(path)
+	if err != nil {
+		return nil, err
+	}
+	resolvedHostPath = PreserveBasePath(path, resolvedHostPath)
+
+	statInfo, err := os.Stat(resolvedHostPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, ENOENT
+		}
+		return nil, err
+	}
+
+	return &FileInfo{
+		Name:       statInfo.Name(),
+		Size:       statInfo.Size(),
+		Mode:       statInfo.Mode(),
+		ModTime:    statInfo.ModTime(),
+		IsDir:      statInfo.IsDir(),
+		LinkTarget: resolvedHostPath,
+	}, nil
+}
+
+// PreserveBasePath makes sure that the original base path (e.g., "/" or "./")
+// is preserved.  The filepath API among tends to clean up a bit too much but
+// we *must* preserve this data by all means.
+func PreserveBasePath(original, resolved string) string {
+	// Handle "/"
+	if strings.HasSuffix(original, "/") {
+		if !strings.HasSuffix(resolved, "/") {
+			resolved += "/"
+		}
+		return resolved
+	}
+
+	// Handle "/."
+	if strings.HasSuffix(original, "/.") {
+		if strings.HasSuffix(resolved, "/") { // could be root!
+			resolved += "."
+		} else if !strings.HasSuffix(resolved, "/.") {
+			resolved += "/."
+		}
+		return resolved
+	}
+
+	return resolved
+}