1{...}: {
 2  programs.ssh = {
 3    enable = true;
 4    enableDefaultConfig = false;
 5
 6    matchBlocks = {
 7      "*".addKeysToAgent = "yes";
 8      "github.com" = {
 9        # "Using SSH over the HTTPS port for GitHub"
10        # "(port 22 is banned by some proxies / firewalls)"
11        hostname = "ssh.github.com";
12        port = 443;
13        user = "git";
14
15        # Specifies that ssh should only use the identity file explicitly configured above
16        # required to prevent sending default identity files first.
17        identitiesOnly = true;
18      };
19    };
20  };
21}