[Fix] nvm_normalize_lts: switch from expr to case

avoids `expr: warning: ^lts/-[1-9][0-9]*: using ^ as the first character of a basic regular expression is not portable; it is ignored`

nvm.sh

@@ -756,23 +756,31 @@ nvm_normalize_lts() {
  local LTS
  LTS="${1-}"
 
- if [ "$(expr "${LTS}" : '^lts/-[1-9][0-9]*$')" -gt 0 ]; then
- local N
- N="$(echo "${LTS}" | cut -d '-' -f 2)"
- N=$((N+1))
- local NVM_ALIAS_DIR
- NVM_ALIAS_DIR="$(nvm_alias_path)"
- local RESULT
- RESULT="$(command ls "${NVM_ALIAS_DIR}/lts" | command tail -n "${N}" | command head -n 1)"
- if [ "${RESULT}" != '*' ]; then
- nvm_echo "lts/${RESULT}"
- else
- nvm_err 'That many LTS releases do not exist yet.'
- return 2
- fi
- else
- nvm_echo "${LTS}"
- fi
+ case "${LTS}" in
+ lts/-[123456789] | lts/-[123456789][0123456789]*)
+ local N
+ N="$(echo "${LTS}" | cut -d '-' -f 2)"
+ ( N=$(( N+1)) ; ) 2>/dev/null
+ # shellcheck disable=SC2181
+ if [ $? -ne 0 ]; then
+ nvm_echo "${LTS}"
+ return 0
+ fi
+ local NVM_ALIAS_DIR
+ NVM_ALIAS_DIR="$(nvm_alias_path)"
+ local RESULT
+ RESULT="$(command ls "${NVM_ALIAS_DIR}/lts" | command tail -n "${N}" | command head -n 1)"
+ if [ "${RESULT}" != '*' ]; then
+ nvm_echo "lts/${RESULT}"
+ else
+ nvm_err 'That many LTS releases do not exist yet.'
+ return 2
+ fi
+ ;;
+ *)
+ nvm_echo "${LTS}"
+ ;;
+ esac
 }
 
 nvm_ensure_version_prefix() {