added build function using svn

bin/ruby-build

@@ -96,6 +96,10 @@ install_git() {
   install_package_using "git" 2 $*
 }
 
+install_svn() {
+ install_package_using "svn" 2 $*
+}
+
 install_package_using() {
   local package_type="$1"
   local package_type_nargs="$2"
@@ -159,6 +163,21 @@ fetch_git() {
   fi
 }
 
+fetch_svn() {
+  local package_name="$1"
+  local svn_url="$2"
+  local svn_rev="$3"
+
+  echo "Checkout ${svn_url}..." >&2
+
+  if type svn &>/dev/null; then
+    svn co -r "$svn_rev" "$svn_url" "${package_name}" >&4 2>&1
+  else
+    echo "error: please install \`svn\` and try again" >&2
+    exit 1
+  fi
+}
+
 build_package() {
   local package_name="$1"
   shift