Skip building documentation when we lack xsltproc

Previously, trying to build from SVN without xsltproc installed would
get you errors like:

  --xinclude -o changes-2.0.1.html changes-2.0.1.xml
  --xinclude:No such file or directory

which is quite confusing.

We now rather just skip the docs completely if we can't find any
xsltproc.  If we actually do need to rebuild the docs (which should
only happen when running make dist), we error out with a useful error
message.



git-svn-id: http://www.varnish-cache.org/svn/trunk@4330 d4fa192b-c00b-0410-8231-f00ffab90ce4

configure.ac

@@ -24,7 +24,11 @@ AC_PROG_CPP
 AC_PROG_INSTALL
 AC_PROG_LIBTOOL
 AC_PROG_MAKE_SET
-AC_CHECK_PROGS(XSLTPROC, [xsltproc])
+AC_CHECK_PROGS(XSLTPROC, [xsltproc], "no")
+if test "x$XSLTPROC" = "xno"; then
+   AC_MSG_WARN([xsltproc not found – not building documentation])
+fi
+AM_CONDITIONAL(HAVE_XSLTPROC,[test "x$XSLTPROC" != "xno"])
 
 # Checks for libraries.
 save_LIBS="${LIBS}"

doc/Makefile.am

@@ -17,17 +17,26 @@ XML = \
 	changes-1.0.3-1.0.4.xml \
 	${CHANGELOGS:.html=.xml}
 
+if HAVE_XSLTPROC
 all: ${CHANGELOGS}
+endif
 
 EXTRA_DIST = ${CHANGELOGS} ${XML} \
 	changes.css changes-html.xsl \
 	getting-started.html
 
 CLEANFILES = ${CHANGELOGS}
-
 SUFFIXES = .xml .html
 
 .xml.html:
+if HAVE_XSLTPROC
 	${XSLTPROC} --xinclude -o $@ $<
+else
+	@echo "========================================"
+	@echo "You need xsltproc installed to make dist"
+	@echo "========================================"
+	@false
+endif
 
 ${CHANGELOGS}: changes-html.xsl
+