nixpkgs doc: add format Make target

doc/Makefile

@@ -1,12 +1,17 @@
 MD_TARGETS=$(addsuffix .xml, $(basename $(wildcard ./*.md ./**/*.md)))
 
 .PHONY: all
-all: validate out/html/index.html out/epub/manual.epub
+all: validate format out/html/index.html out/epub/manual.epub
 
 .PHONY: debug
 debug:
 	nix-shell --run "xmloscopy --docbook5 ./manual.xml ./manual-full.xml"
 
+.PHONY: format
+format:
+	find . -iname '*.xml' -type f -print0 | xargs -0 -I{} -n1 \
+		xmlformat --config-file "$$XMLFORMAT_CONFIG" -i {}
+
 .PHONY: clean
 clean:
 	rm -f ${MD_TARGETS} .version manual-full.xml

doc/default.nix

@@ -7,7 +7,7 @@ in
 pkgs.stdenv.mkDerivation {
   name = "nixpkgs-manual";
 
-  buildInputs = with pkgs; [ pandoc libxml2 libxslt zip jing ];
+  buildInputs = with pkgs; [ pandoc libxml2 libxslt zip jing  xmlformat ];
 
   src = ./.;
 
@@ -18,6 +18,7 @@ pkgs.stdenv.mkDerivation {
   HIGHLIGHTJS = pkgs.documentation-highlighter;
   XSL = "${pkgs.docbook5_xsl}/xml/xsl";
   RNG = "${pkgs.docbook5}/xml/rng/docbook/docbook.rng";
+  XMLFORMAT_CONFIG = ../nixos/doc/xmlformat.conf;
   xsltFlags = lib.concatStringsSep " " [
     "--param section.autolabel 1"
     "--param section.label.includes.component.label 1"

doc/shell.nix

@@ -1,4 +1,5 @@
 { pkgs ? import ../. {} }:
 (import ./default.nix).overrideAttrs (x: {
   buildInputs = x.buildInputs ++ [ pkgs.xmloscopy ];
+
 })