Configure ssh to forward GPG agent.

.ssh/config

@@ -3,7 +3,7 @@ AddKeysToAgent			yes
 ConnectTimeout			30
 # Removed as this prevents use of ^Z suspension.
 # ControlMaster			auto
-# ControlPath			~/.ssh/%u@%l->%r@%h:%p
+# ControlPath			${HOME}/.ssh/%u@%l->%r@%h:%p
 # ControlPersist		7200
 ExitOnForwardFailure		yes
 HashKnownHosts			no
@@ -17,14 +17,14 @@ Host zapp
   Hostname			zapp.opensourcerers.net
   Port				9922
   ForwardAgent			yes
-  RemoteForward			~/.gnupg/S.gpg-agent	~/.gnupg/S.gpg-agent.extra
+  RemoteForward			%d/.gnupg/S.gpg-agent	${HOME}/.gnupg/S.gpg-agent
 
 # Remote servers.
 Host bender fry leela mirror seedbox
-  HostName			%n.hosts.slackware.network
+  HostName			%h.hosts.slackware.network
   Port				9922
   ForwardAgent			yes
-  RemoteForward			~/.gnupg/S.gpg-agent	~/.gnupg/S.gpg-agent.extra
+  RemoteForward			%d/.gnupg/S.gpg-agent	${HOME}/.gnupg/S.gpg-agent
 
 Host esx0.hosts.slackware.network esx1.hosts.slackware.network
   Port				22
@@ -32,24 +32,22 @@ Host esx0.hosts.slackware.network esx1.hosts.slackware.network
 Host *.hosts.slackware.network
   Port				9922
   ForwardAgent			yes
-  RemoteForward			~/.gnupg/S.gpg-agent	~/.gnupg/S.gpg-agent.extra
+  RemoteForward			%d/.gnupg/S.gpg-agent	${HOME}/.gnupg/S.gpg-agent
 
 # Home stuff.
 Host afterdark.org.uk
   Port				6722
   ForwardAgent			yes
-  RemoteForward			~/.gnupg/S.gpg-agent	~/.gnupg/S.gpg-agent.extra
 
 Host phil lil tommy-wifi
   ForwardAgent			yes
   ForwardX11Trusted		yes
-  RemoteForward			~/.gnupg/S.gpg-agent	~/.gnupg/S.gpg-agent.extra
 
 Host full-* build-* clone-*
   ForwardAgent			yes
-  RemoteForward			~/.gnupg/S.gpg-agent	~/.gnupg/S.gpg-agent.extra
+  RemoteForward			/run/user/0/gnupg/S.gpg-agent	${HOME}/.gnupg/S.gpg-agent
   User				root
 
 # GitHub.
 Host github.com
-  IdentityFile			~/.ssh/id_ed25519_github
+  IdentityFile			${HOME}/.ssh/id_ed25519_github