Building git documentation on cygwin

I had some trouble building the git documentation under cygwin. The issue is apparently that on cygwin the xmlcatalog is not set up to allow offline builds. In my case, my cygwin install was missing an /etc/xml/catalog file. The simplest fix in this case is to create a this file manually:

<?xml version="1.0"?>
<!DOCTYPE catalog PUBLIC 
   "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 
   "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"
>
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
  <rewriteURI 
     uriStartString = "http://docbook.sourceforge.net/release/xsl/current" 
     rewritePrefix = "/usr/share/sgml/docbook/xsl-stylesheets"
  />
  <rewriteURI 
     uriStartString="http://www.oasis-open.org/docbook/xml/4.5" 
     rewritePrefix="/usr/share/sgml/docbook/xml-dtd-4.5"
  />
</catalog>

Alternatively, you can update an existing file with:

xmlcatalog --noout \
   --add rewriteURI \
        http://docbook.sourceforge.net/release/xsl/current \
        /usr/share/sgml/docbook/xsl-stylesheets \
   /etc/xml/catalog
xmlcatalog --noout \
   --add rewriteURI \
         http://www.oasis-open.org/docbook/xml/4.5/xsl/current \
         /usr/share/sgml/docbook/xml-dtd-4.5 \
   /etc/xml/catalog