Preferred Chain

Using --preferred-chain to select alternate chain.

If the ACME CA provides multiple cert chain, you can use --preferred-chain to select one. Otherwise, it will get the default chain.

1. For Letsencrpt.org Staging Server:

   There are 2 chains provided:

   Name	Default
   Fake LE Root X1	Yes
   Fake LE Root X2	No

   You select the ca like:

acme.sh  --issue -d example.com .....     --preferred-chain  "Fake LE Root X2"

2. For Letsencrypt.org Production server:

   There are 2 chains provided:

   Name	Default
   DST Root CA X3	Yes
   ISRG Root X1	No

   You select the ca like:

acme.sh  --issue -d example.com .....     --preferred-chain  "ISRG Root X1"