support "--set-default-chain", fix https://github.com/acmesh-official/acme.sh/issues/3717

acme.sh

@@ -6547,6 +6547,8 @@ Commands:
   --deactivate             Deactivate the domain authz, professional use.
   --set-default-ca         Used with '--server', Set the default CA to use.
                            See: $_SERVER_WIKI
+  --set-default-chain      Set the default preferred chain for a CA.
+                           See: $_PREFERRED_CHAIN_WIKI
 
 
 Parameters:
@@ -6833,6 +6835,18 @@ setdefaultca() {
   _info "Changed default CA to: $(__green "$ACME_DIRECTORY")"
 }
 
+#preferred-chain
+setdefaultchain() {
+  _initpath
+  _preferred_chain="$1"
+  if [ -z "$_preferred_chain" ]; then
+    _err "Please give a '--preferred-chain value' value."
+    return 1
+  fi
+  mkdir -p "$CA_DIR"
+  _savecaconf "DEFAULT_PREFERRED_CHAIN" "$_preferred_chain"
+}
+
 _process() {
   _CMD=""
   _domain=""
@@ -6984,6 +6998,9 @@ _process() {
     --set-default-ca)
       _CMD="setdefaultca"
       ;;
+    --set-default-chain)
+      _CMD="setdefaultchain"
+      ;;
     -d | --domain)
       _dvalue="$2"
 
@@ -7514,6 +7531,9 @@ _process() {
   setdefaultca)
     setdefaultca
     ;;
+  setdefaultchain)
+    setdefaultchain "$_preferred_chain"
+    ;;
   *)
     if [ "$_CMD" ]; then
       _err "Invalid command: $_CMD"