Merged the two expressions to single regex

sbin/common/common.sh

@@ -20,16 +20,14 @@ function setOpenJdkVersion() {
   # The argument passed here have actually very strict format of jdk8, jdk8u..., jdk
   # the build may fail later if this is not honoured.
   # If your repository has a different name, you can use --version or build from dir/snapshot
-  local forest_name_check1=0
-  local forest_name_check2=0
-  echo "$forest_name" | grep "^jdk[0-9]\\{1,3\\}[u]\\{0,1\\}$" >/dev/null || forest_name_check1=$?
-  echo "$forest_name" | grep "^jdk$" >/dev/null || forest_name_check2=$?
-  if [ ${forest_name_check1} -ne 0 ] && [ ${forest_name_check2} -ne 0 ]; then
+  local forest_name_check=0
+  echo "$forest_name" | grep "^\(jdk\|jdk[0-9]\\{1,3\\}[u]\\{0,1\\}\)$" >/dev/null || forest_name_check=$?
+  if [ ${forest_name_check} -ne 0 ]; then
     echo "The mandatory repo argument has a very strict format 'jdk[0-9]{1,3}[u]{0,1}' or just plain 'jdk' for tip. '$forest_name' does not match."
     echo "This can be worked around by using '--version jdkXYu'. If set (and matching) then the main argument can have any value."
-    exit 1
-  fi
 
+  fi
+}
   # Derive the openjdk_core_version from the forest name.
   local openjdk_core_version=${forest_name}
   if [[ ${forest_name} == *u ]]; then