chore(kb/gpg+ssh): improve article sections and examples about gnupg integration with ssh

examples/ssh/ssh_config

@@ -86,3 +86,6 @@ HashKnownHosts       no
 ServerAliveCountMax  2
 ServerAliveInterval  300
 UseKeyChain          yes
+
+# GnuPG integration
+IdentityAgent  ~/.gnupg/S.gpg-agent.ssh

knowledge base/gnupg.md

@@ -379,10 +379,11 @@ Now tell SSH how to access `gpg-agent` by setting the value of the `SSH_AUTH_SOC
 Alternatively, and for a more permanent solution, set the option in the `.ssh/config` file:
 
 ```sh
-export SSH_AUTH_SOCK=$(gpgconf --list-dirs agent-ssh-socket)
+export SSH_AUTH_SOCK=$(gpgconf --list-dirs 'agent-ssh-socket')
 
 # alternative
-echo "IdentityAgent $(gpgconf --list-dirs agent-ssh-socket)" >> ~'/.ssh/config'
+echo "\nIdentityAgent $(gpgconf --list-dirs 'agent-ssh-socket')" \
+| tee -a ~'/.ssh/config'
 ```
 
 Now you can launch the gpg agent:

knowledge base/ssh.md

@@ -8,6 +8,7 @@
 1. [Client configuration](#client-configuration)
    1. [Append domains to a hostname before attempting to check if they exist](#append-domains-to-a-hostname-before-attempting-to-check-if-they-exist)
    1. [Optimize connection handling](#optimize-connection-handling)
+   1. [Integrate with GnuPG](#integrate-with-gnupg)
 1. [Server configuration](#server-configuration)
    1. [Change port](#change-port)
    1. [Disable password authentication](#disable-password-authentication)
@@ -229,6 +230,22 @@ ControlPath ~/.ssh/control-%C
 ControlPersist 30s
 ```
 
+### Integrate with GnuPG
+
+```sh
+# In BASH and alike.
+export SSH_AUTH_SOCK=$(gpgconf --list-dirs 'agent-ssh-socket')
+
+# In FISH.
+set -x 'SSH_AUTH_SOCK' (gpgconf --list-dirs 'agent-ssh-socket')
+```
+
+```ssh-config
+# In ~/.ssh/config.
+# Value is from `gpgconf --list-dirs 'agent-ssh-socket'`.
+IdentityAgent ~/.gnupg/S.gpg-agent.ssh
+```
+
 ## Server configuration
 
 Config file defaults to `/etc/ssh/sshd_config`.<br/>