Use `nvm_num_version_groups` in `nvm_ls`

nvm.sh

@@ -247,14 +247,18 @@ nvm_ls() {
     return
   fi
   # If it looks like an explicit version, don't do anything funny
-  if [ `expr "$PATTERN" : "v[0-9]*\.[0-9]*\.[0-9]*$"` != 0 ]; then
+  if [ "~$(echo "$PATTERN" | cut -c1-1)" = "~v" ] &&  [ "~$(nvm_num_version_groups "$PATTERN")" = "~3" ]; then
     if [ -d "$(nvm_version_path "$PATTERN")" ]; then
       VERSIONS="$PATTERN"
     fi
   else
     PATTERN=$(nvm_format_version $PATTERN)
-    if [ `expr "$PATTERN" : "v[0-9]*\.[0-9]*$"` != 0 ]; then
+    if [ "~$PATTERN" != "~system" ]; then
-      PATTERN="$PATTERN."
+      local NUM_VERSION_GROUPS
+      NUM_VERSION_GROUPS="$(nvm_num_version_groups "$PATTERN")"
+      if [ "~$NUM_VERSION_GROUPS" = "~2" ] || [ "~$NUM_VERSION_GROUPS" = "~1" ]; then
+        PATTERN="$(echo "$PATTERN" | sed -e 's/\.*$//g')."
+      fi
     fi
     if [ -d "$(nvm_version_dir new)" ]; then
       VERSIONS=`find "$(nvm_version_dir new)/" "$(nvm_version_dir old)/" -maxdepth 1 -type d -name "$PATTERN*" -exec basename '{}' ';' \