nix-bitcoin.nix: add `defaultText` (automatic)

This enables generating module option documentation.

This commit was genereated by running the following script inside the
repo root dir:

def add_default_text(file)
  src = File.read(file)
  src2 = src.gsub(/( = mkOption\s+\{[^{]*?)(\n\s+default = )(.*?);$(.*?\})/m) do |str|
    pre, defaultVar, default, post = Regexp.last_match.captures
    replacement =
      if !post.include?('defaultText =')
        if default =~ /\bpkgs\b/
          defaultText = default.lines.length == 1 ? default : "(See source)"
          "#{pre}#{defaultVar}#{default};#{defaultVar.sub('default', 'defaultText')}#{defaultText.inspect};#{post}"
        end
      end
    replacement or str
  end
  File.write(file, src2) if src2 != src
end

Dir["modules/**/*.nix"].each do |f|
  next if File.basename(f) == "nix-bitcoin.nix"
  add_default_text f
end

modules/bitcoind.nix

@@ -57,6 +57,7 @@ let
       package = mkOption {
         type = types.package;
         default = config.nix-bitcoin.pkgs.bitcoind;
+        defaultText = "config.nix-bitcoin.pkgs.bitcoind";
         description = "The package providing bitcoin binaries.";
       };
       extraConfig = mkOption {
@@ -265,6 +266,7 @@ let
         default = pkgs.writeScriptBin "bitcoin-cli" ''
           exec ${cfg.package}/bin/bitcoin-cli -datadir='${cfg.dataDir}' "$@"
         '';
+        defaultText = "(See source)";
         description = "Binary to connect with the bitcoind instance.";
       };
       tor = nbLib.tor;

modules/btcpayserver.nix

@@ -21,6 +21,7 @@ let
                     config.nix-bitcoin.pkgs.btcpayserver.override { altcoinSupport = true; }
                   else
                     config.nix-bitcoin.pkgs.btcpayserver;
+        defaultText = "(See source)";
         description = "The package providing btcpayserver binaries.";
       };
       dataDir = mkOption {
@@ -69,6 +70,7 @@ let
       package = mkOption {
         type = types.package;
         default = config.nix-bitcoin.pkgs.nbxplorer;
+        defaultText = "config.nix-bitcoin.pkgs.nbxplorer";
         description = "The package providing nbxplorer binaries.";
       };
       address = mkOption {

modules/clightning-plugins/clboss.nix

@@ -17,6 +17,7 @@ let cfg = config.services.clightning.plugins.clboss; in
     package = mkOption {
       type = types.package;
       default = config.nix-bitcoin.pkgs.clboss;
+      defaultText = "config.nix-bitcoin.pkgs.clboss";
       description = "The package providing clboss binaries.";
     };
   };

modules/clightning.nix

@@ -69,6 +69,7 @@ let
       default = pkgs.writeScriptBin "lightning-cli" ''
         ${nbPkgs.clightning}/bin/lightning-cli --lightning-dir='${cfg.dataDir}' "$@"
       '';
+      defaultText = "(See source)";
       description = "Binary to connect with the clightning instance.";
     };
     getPublicAddressCmd = mkOption {

modules/lightning-loop.nix

@@ -27,6 +27,7 @@ let
     package = mkOption {
       type = types.package;
       default = config.nix-bitcoin.pkgs.lightning-loop;
+      defaultText = "config.nix-bitcoin.pkgs.lightning-loop";
       description = "The package providing lightning-loop binaries.";
     };
     dataDir = mkOption {
@@ -54,6 +55,7 @@ let
         --macaroonpath '${cfg.dataDir}/${network}/loop.macaroon' \
         --tlscertpath '${secretsDir}/loop-cert' "$@"
       '';
+      defaultText = "(See source)";
       description = "Binary to connect with the lightning-loop instance.";
     };
     tor = nbLib.tor;

modules/lightning-pool.nix

@@ -27,6 +27,7 @@ let
     package = mkOption {
       type = types.package;
       default = config.nix-bitcoin.pkgs.lightning-pool;
+      defaultText = "config.nix-bitcoin.pkgs.lightning-pool";
       description = "The package providing lightning-pool binaries.";
     };
     dataDir = mkOption {
@@ -54,6 +55,7 @@ let
           --network ${network} \
           --basedir '${cfg.dataDir}' "$@"
       '';
+      defaultText = "(See source)";
       description = "Binary to connect with the lightning-pool instance.";
     };
     tor = nbLib.tor;

modules/liquid.nix

@@ -148,12 +148,14 @@ let
         default = pkgs.writeScriptBin "elements-cli" ''
           ${nbPkgs.elementsd}/bin/elements-cli -datadir='${cfg.dataDir}' "$@"
         '';
+        defaultText = "(See source)";
         description = "Binary to connect with the liquidd instance.";
       };
       swapCli = mkOption {
         default = pkgs.writeScriptBin "liquidswap-cli" ''
           ${nbPkgs.liquid-swap}/bin/liquidswap-cli -c '${cfg.dataDir}/elements.conf' "$@"
         '';
+        defaultText = "(See source)";
         description = "Binary for managing liquid swaps.";
       };
       tor = nbLib.tor;

modules/lnd-rest-onion-service.nix

@@ -15,6 +15,7 @@ let
     package = mkOption {
       type = types.package;
       default = config.nix-bitcoin.pkgs.lndconnect;
+      defaultText = "config.nix-bitcoin.pkgs.lndconnect";
       description = "The package providing lndconnect binaries.";
     };
   };

modules/lnd.nix

@@ -81,6 +81,7 @@ let
     package = mkOption {
       type = types.package;
       default = config.nix-bitcoin.pkgs.lnd;
+      defaultText = "config.nix-bitcoin.pkgs.lnd";
       description = "The package providing lnd binaries.";
     };
     cli = mkOption {
@@ -92,6 +93,7 @@ let
             --tlscertpath '${cfg.certPath}' \
             --macaroonpath '${networkDir}/admin.macaroon' "$@"
         '';
+      defaultText = "(See source)";
       description = "Binary to connect with the lnd instance.";
     };
     getPublicAddressCmd = mkOption {