autocrap magic to find varnish.m4 via pkg-config

Fixes #6 (github issue)

Makefile.am

@@ -1,4 +1,4 @@
-ACLOCAL_AMFLAGS = -I m4
+ACLOCAL_AMFLAGS = -I m4 -I ${LIBVARNISHAPI_DATAROOTDIR}/aclocal
 
 SUBDIRS = src
 

README.rst

@@ -51,14 +51,18 @@ using the ``varnishtest`` tool.
 Building requires the Varnish header files and uses pkg-config to find
 the necessary paths.
 
-If you have installed Varnish to a non-standard directory, you may need to
-override PKG_CONFIG_PATH so configure can find varnishapi.pc.
-
 Usage::
 
  ./autogen.sh
  ./configure
 
+If you have installed Varnish to a non-standard directory, call
+``autogen.sh`` and ``configure`` with ``PKG_CONFIG_PATH`` pointing to
+the appropriate path. For example, when varnishd configure was called
+with ``--prefix=$PREFIX``, use
+
+ PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig
+ export PKG_CONFIG_PATH
 
 Make targets:
 
@@ -68,11 +72,18 @@ Make targets:
 * make distcheck - run check and prepare a tarball of the vmod.
 
 In your VCL you could then use this vmod along the following lines::
-        
+
         import example;
 
         sub vcl_deliver {
                 # This sets resp.http.hello to "Hello, World"
                 set resp.http.hello = example.hello("World");
         }
 
+COMMON PROBLEMS
+===============
+
+* configure: error: Need varnish.m4 -- see README.rst
+
+  Check if ``PKG_CONFIG_PATH`` has been set correctly before calling
+  ``autogen.sh`` and ``configure``

autogen.sh

@@ -37,7 +37,9 @@ fi
 
 set -ex
 
-aclocal -I m4
+# check for varnishapi.m4 in custom paths
+dataroot=$(pkg-config --variable=datarootdir varnishapi)
+aclocal -I m4 -I ${dataroot}/aclocal
 $LIBTOOLIZE --copy --force
 autoheader
 automake --add-missing --copy --foreign

configure.ac

@@ -2,6 +2,7 @@ AC_PREREQ(2.59)
 AC_COPYRIGHT([Copyright (c) 2011-2015 Varnish Software AS])
 AC_INIT([libvmod-example], [trunk])
 AC_CONFIG_MACRO_DIR([m4])
+m4_ifndef([VARNISH_VMOD_INCLUDES], AC_MSG_ERROR([Need varnish.m4 -- see README.rst]))
 AC_CONFIG_SRCDIR(src/vmod_example.vcc)
 AM_CONFIG_HEADER(config.h)
 
@@ -33,8 +34,9 @@ AM_CONDITIONAL(HAVE_RST2MAN, [test "x$RST2MAN" != "xno"])
 AC_HEADER_STDC
 AC_CHECK_HEADERS([sys/stdlib.h])
 
-
 PKG_CHECK_MODULES([libvarnishapi], [varnishapi])
+PKG_CHECK_VAR([LIBVARNISHAPI_DATAROOTDIR], [varnishapi], [datarootdir])
+AC_SUBST([LIBVARNISHAPI_DATAROOTDIR])
 
 # Varnish include files tree
 VARNISH_VMOD_INCLUDES