Allows LoopbackFileSystem to use symlinks to directories

as root. This is important especially when LoopbackFileSystem
is used in combination with AutoUnionFs and the root one of
the overlays is a symlink - in that case we don't want to
link out of the overlay directory structure.

fuse/loopback.go

@@ -32,9 +32,16 @@ func (me *LoopbackFileSystem) GetPath(relPath string) string {
 	return filepath.Join(me.Root, relPath)
 }
 
-func (me *LoopbackFileSystem) GetAttr(name string, context *Context) (*os.FileInfo, Status) {
+func (me *LoopbackFileSystem) GetAttr(name string, context *Context) (fi *os.FileInfo, code Status) {
 	fullPath := me.GetPath(name)
-	fi, err := os.Lstat(fullPath)
+	var err os.Error = nil
+	if name == "" {
+		// When GetAttr is called for the toplevel directory, we always want
+		// to look through symlinks.
+		fi, err = os.Stat(fullPath)
+	} else {
+		fi, err = os.Lstat(fullPath)
+	}
 	if err != nil {
 		return nil, OsErrorToErrno(err)
 	}

fuse/loopback_test.go

@@ -666,3 +666,27 @@ func TestStatFs(t *testing.T) {
 		t.Error("Mismatch", s1, s2)
 	}
 }
+
+func TestOriginalIsSymlink(t *testing.T) {
+	tmpDir := MakeTempDir()
+	defer os.RemoveAll(tmpDir)
+	orig := tmpDir + "/orig"
+	err := os.Mkdir(orig, 0755)
+	CheckSuccess(err)
+	link := tmpDir + "/link"
+	mnt := tmpDir + "/mnt"
+	err = os.Mkdir(mnt, 0755)
+	CheckSuccess(err)
+	err = os.Symlink("orig", link)
+	CheckSuccess(err)
+
+	fs := NewLoopbackFileSystem(link)
+	state, _, err := MountFileSystem(mnt, fs, nil)
+	CheckSuccess(err)
+	defer state.Unmount()
+
+	go state.Loop(false)
+
+	_, err = os.Lstat(mnt)
+	CheckSuccess(err)
+}