Fix Glob handling of backslashes

\m\a\t\c\h\.\g\o would be interpreted as a literal path, because the
backslash was missing in the check.

client_integration_test.go

@@ -1882,6 +1882,7 @@ var globTests = []struct {
 	{"match.go", "match.go"},
 	{"mat?h.go", "match.go"},
 	{"ma*ch.go", "match.go"},
+	{`\m\a\t\c\h\.\g\o`, "match.go"},
 	{"../*/match.go", "../sftp/match.go"},
 }
 

match.go

@@ -133,6 +133,5 @@ func Join(elem ...string) string {
 // hasMeta reports whether path contains any of the magic characters
 // recognized by Match.
 func hasMeta(path string) bool {
-	// TODO(niemeyer): Should other magic characters be added here?
-	return strings.ContainsAny(path, "*?[")
+	return strings.ContainsAny(path, "\\*?[")
 }