nixos/man: prevent duplication of options

libxslt 1.1.35 fixed conflict resolution for templates to match the specification.
This uncovered a bug in docbook-xsl (docbook/xslt10-stylesheets#240),
which causes option names to be duplicated into the option descriptions.

Let’s resolve the conflict by patching the stylesheets.

Fixes: NixOS#166304

nixos/doc/manual/default.nix

@@ -14,6 +14,10 @@ with pkgs;
 let
   lib = pkgs.lib;
 
+  docbook_xsl_ns = pkgs.docbook-xsl-ns.override {
+    withManOptDedupPatch = true;
+  };
+
   # We need to strip references to /nix/store/* from options,
   # including any `extraSources` if some modules came from elsewhere,
   # or else the build will fail.

pkgs/data/sgml+xml/stylesheets/xslt/docbook-xsl/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, substituteAll, fetchurl, fetchpatch, findXMLCatalogs, writeScriptBin, ruby, bash }:
+{ lib, stdenv, substituteAll, fetchurl, fetchpatch, findXMLCatalogs, writeScriptBin, ruby, bash, withManOptDedupPatch ? false }:
 
 let
 
@@ -36,6 +36,10 @@ let
           src = ./catalog-legacy-uris.patch;
           inherit legacySuffix suffix version;
         })
+      ] ++ lib.optionals withManOptDedupPatch [
+        # Fixes https://github.com/NixOS/nixpkgs/issues/166304
+        # https://github.com/docbook/xslt10-stylesheets/pull/241
+        ./fix-man-options-duplication.patch
       ];
 
       propagatedBuildInputs = [ findXMLCatalogs ];

pkgs/data/sgml+xml/stylesheets/xslt/docbook-xsl/fix-man-options-duplication.patch

@@ -0,0 +1,11 @@
+--- a/manpages/lists.xsl
++++ b/manpages/lists.xsl
+@@ -110,7 +110,7 @@
+   <xsl:text>.RE&#10;</xsl:text>
+ </xsl:template>
+
+-<xsl:template match="d:varlistentry/d:term"/>
++<xsl:template match="d:varlistentry/d:term" priority="1"/>
+ <xsl:template match="d:glossentry/d:glossterm"/>
+
+ <xsl:template match="d:variablelist[ancestor::d:listitem or ancestor::d:step or ancestor::d:glossdef]|