Meta/docbuild-8: make it easier to compare AsciiDoc 7 and 8 output

docbuild-8.sh

@@ -1,6 +1,18 @@
 #!/bin/sh
 
-PATH=~/asciidoc/bin:$PATH \
-make prefix=/var/tmp/asciidoc8 \
-	WEBDOC_DEST=/var/tmp/asciidoc8/webdoc \
+case "$1" in
+7)
+	V=7
+	EXTRA=
+	;;
+8 | '')
+	V=8
+	PATH=~/asciidoc/bin:$PATH
+	EXTRA=ASCIIDOC8=YesPlease
+	;;
+esac
+
+make prefix=/var/tmp/asciidoc$V \
+	WEBDOC_DEST=/var/tmp/asciidoc$V/webdoc \
+	$EXTRA \
 	install install-webdoc