textproc/xmlstarlet: create docs variant

textproc/xmlstarlet/Portfile

@@ -23,18 +23,14 @@ master_sites        sourceforge:project/xmlstar/xmlstarlet/${version}
 checksums           rmd160  16ca33aa94cd9cb45ef0635526ed07243c4819db \
                     sha256  15d838c4f3375332fd95554619179b69e4ec91418a3a5296e7c631b7ed19e7ca
 
-depends_build       port:docbook-xsl-ns \
-                    port:fop \
-                    port:ghostscript
-
 depends_lib         port:libxml2 port:libxslt port:libiconv
 
 configure.args      --disable-silent-rules \
                     --with-libxml-prefix=${prefix} \
                     --with-libxslt-prefix=${prefix} \
                     --with-libiconv-prefix=${prefix} \
                     --mandir=${prefix}/share/man \
-                    --enable-build_docs \
+                    --disable-build_docs \
                     --program-transform-name=s/xml$/${name}/
 
 build.target        clean-doc all
@@ -57,6 +53,15 @@ post-destroot {
     file copy ${worksrcpath}/examples ${destroot}${prefix}/share/${name}
 }
 
+variant docs description {Enable documentation} {
+    depends_build-append    port:docbook-xsl-ns \
+                            port:fop \
+                            port:ghostscript
+
+    configure.args-delete --disable-build_docs
+    configure.args-append --enable-build_docs
+}
+
 notes "
 Some ${name} documentation files refer to the program name as \"xml\" but\
 in MacPorts the program is installed as \"${name}\".