Reuse blacklisting code in exp_archive.

client/internal/common/filesystem_view.go

Index: client/internal/common/filesystem_view.go
diff --git a/client/internal/common/filesystem_view.go b/client/internal/common/filesystem_view.go
index 42bd5022495d6430ea7f59dbedebafaac95ececb..5f60a831559a828c81d7d87c5a813181d3c92b72 100644
--- a/client/internal/common/filesystem_view.go
+++ b/client/internal/common/filesystem_view.go
@@ -16,6 +16,7 @@ package common
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 )
 
@@ -79,3 +80,16 @@ func match(pattern, name string) bool {
 	matched, _ := filepath.Match(pattern, name)
 	return matched
 }
+
+// WalkFuncSkipFile is a helper for implemenations of filepath.WalkFunc. The
+// value that it returns may in turn be returned by the WalkFunc implementaiton
+// to indicate that file should be skipped.
+func WalkFuncSkipFile(file os.FileInfo) error {
+	if file.IsDir() {
+		return filepath.SkipDir
+	}
+	// If we were to return SkipDir for a file, it would cause
+	// filepath.Walk to skip the file's containing directory, which we do
+	// not want (see https://golang.org/pkg/path/filepath/#WalkFunc).
+	return nil
+}