Use regexp.MatchString rather regexp.FindString() != "".

Change-Id: I12f4f7a6e4ac96be33a00bcb8fd0154735b3225b

fs/gitilesfs.go

diff --git a/fs/gitilesfs.go b/fs/gitilesfs.go
index 1c0ee46..8f4287d 100644
--- a/fs/gitilesfs.go
+++ b/fs/gitilesfs.go
@@ -396,7 +396,7 @@
 		clone := r.opts.CloneURL != ""
 		if clone {
 			for _, e := range r.opts.CloneOption {
-				if e.RE.FindString(p) != "" {
+				if e.RE.MatchString(p) {
 					clone = e.Clone
 					break
 				}