Support versioning out of git tree in debuild

This adds support for properly tagging the build when cmake is run not
in a git tree, which is the case when building from src-deb.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>

debian/rules

@@ -4,5 +4,12 @@
 # Uncomment this to turn on verbose mode.
 #export DH_VERBOSE=1
 
+DEBIAN_VERSION := $(shell dpkg-parsechangelog | sed -rne "s,^Version: (.*),\1,p")
+DEBIAN_REVISION := $(shell dpkg-parsechangelog | sed -rne "s,^Version: ([0-9.]+)(~|-)(.*),\3,p")
+UPSTREAM_VERSION := $(shell dpkg-parsechangelog | sed -rne "s,^Version: ([0-9.]+)(~|-)(.*),\1,p")
+
 %:
 	dh $@ --buildsystem=cmake --parallel
+
+override_dh_auto_configure:
+	dh_auto_configure -- -DREVISION=$(UPSTREAM_VERSION)