git-refresh: fix expr

* tool/git-refresh (dir): surround by slashes to extract base
  name.  [ruby-dev:50070] [Bug #13424]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58335 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/git-refresh

@@ -24,13 +24,13 @@ url="$1"
 dir="$2"
 shift 2
 if [ -d "$dir" ]; then
-    echo updating `expr "$dir" : '*/\(.*\)'` ...
+    echo updating `expr "/$dir/" : '.*/\([^/][^/]*\)/'` ...
     [ $quiet ] || set -x
     cd "$dir"
     git fetch "$@"
     exec git checkout ${branch:+"$branch"} "$@"
 else
-    echo retrieving `expr "$dir" : '*/\(.*\)'` ...
+    echo retrieving `expr "/$dir/" : '.*/\([^/][^/]*\)/'` ...
     [ $quiet ] || set -x
     exec git clone "$url" "$dir" "$@"
 fi