Added fish support for ssh-agent.

fish/functions/__ssh_agent_is_started.fish

@@ -0,0 +1,23 @@
+function __ssh_agent_is_started -d "check if ssh agent is already started"
+	if test -n "$SSH_CONNECTION"
+		# This is an SSH session
+		ssh-add -l > /dev/null 2>&1
+		if test $status -eq 0 -o $status -eq 1
+			# An SSH agent was forwarded
+			return 0
+		end
+	end
+
+	if begin; test -f "$SSH_ENV"; and test -z "$SSH_AGENT_PID"; end
+		source $SSH_ENV > /dev/null
+	end
+
+	if test -z "$SSH_AGENT_PID"
+		return 1
+	end
+
+	ssh-add -l > /dev/null 2>&1
+	if test $status -eq 2
+		return 1
+	end
+end