Add removeAll to fakeFs

pkg/fs/fakefs.go

@@ -77,6 +77,21 @@ func (fs *fakeFs) MkdirAll(name string) error {
 	return fs.Mkdir(name)
 }
 
+// RemoveAll presumably does rm -r on a path.
+// There's no error.
+func (fs *fakeFs) RemoveAll(name string) error {
+	var toRemove []string
+	for k := range fs.m {
+		if strings.HasPrefix(k, name) {
+			toRemove = append(toRemove, k)
+		}
+	}
+	for _, k := range toRemove {
+		delete(fs.m, k)
+	}
+	return nil
+}
+
 // Open returns a fake file in the open state.
 func (fs *fakeFs) Open(name string) (File, error) {
 	if _, found := fs.m[name]; !found {