Improve vars auto load

[TinCanTech]

This refines the automatic loading of a vars file.

[TinCanTech]

The FINAL stage:

• If the vars in use is within the PKI then it MUST NOT reassign EASYRSA_PKI. Which only effects hard-coded pki/vars.

[TinCanTech]

auto-load result is as follows:

If EASYRSA_VARS_FILE --vars=FILE is set then use it and no auto-load.

Reminder: easyrsa program location is no longer considered a viable place to keep a vars file.

Working directory:

• $PWD/vars is the default.
• NOTE: This vars file is allowed to set the PKI.

Working directory Default PKI:

• $PWD/pki/vars auto-loaded if $PWD/vars does NOT exist.
• Otherwise conflict.
• NOTE: If this vars changes the EASYRSA_PKI then it is a fatal error.

if EASYRSA_PKI --pki-dir=DIR is set then allow auto-load:

• Either $EASYRSA_PKI/vars (User set PKI directory)
• OR $PWD/vars (Working directory)
• If both exist then conflict.
• NOTE: This vars cannot change EASYRSA_PKI because it is already set.

This allows --pki-dir=DIR to auto-load a vars file inside the user set PKI.

How to use vars with multiple PKI directories

Use --vars=FILE:
This will always use ONLY the specified file, which is allowed to set the PKI.

Use --pki-dir=DIR
If no default vars file exists then the PKI vars file will be used.
This file cannot change the PKI in use.

Thus, for a multiple PKI installation with multiple vars files:

./pki-home/vars
./pki-work/vars

The SAFEST use is with --pki-dir=DIR, which can then differentiate between the two vars files shown.

To use --vars=FILE the following setup is required:

./vars.pki-home
./vars.pki-work
./pki-home/
./pki-work/

Use --vars=vars.pki-home to set EASYRSA_PKI to pki-home. etc. This is more prone to user error.

---

Add this to https://github.com/OpenVPN/easy-rsa/blob/master/doc/EasyRSA-Advanced.md