Update function for clone_repo to accept optional argument

Author: JonRowe

ci/script/functions.sh

@@ -16,7 +16,13 @@ fi
 
 function clone_repo {
   if [ ! -d $1 ]; then # don't clone if the dir is already there
-    travis_retry eval "git clone https://github.com/rspec/$1 --depth 1 --branch $MAINTENANCE_BRANCH"
+    if [ -z "$2" ]; then
+      BRANCH_TO_CLONE="$MAINTENANCE_BRANCH"
+    else
+      BRANCH_TO_CLONE="$2"
+    fi
+
+    travis_retry eval "git clone https://github.com/rspec/$1 --depth 1 --branch $BRANCH_TO_CLONE"
   fi;
 }