trivial: debian: calculate version number using git describe again

This will be more representative of what the build actually is
rather than a mismarked tag.

If the checkout doesn't include a tag, fallback to parsing meson.build
though.

contrib/ci/Dockerfile-debian-experimental

@@ -9,6 +9,7 @@ RUN apt-get install -yq --no-install-recommends \
 	fontconfig-config \
 	fonts-dejavu \
 	gir1.2-pango-1.0 \
+	git \
 	gcab \
 	gettext \
 	gobject-introspection \

contrib/ci/Dockerfile-debian-unstable

@@ -8,6 +8,7 @@ RUN apt-get install -yq --no-install-recommends \
 	fontconfig \
 	fontconfig-config \
 	fonts-dejavu \
+	git \
 	gcab \
 	gettext \
 	gir1.2-appstreamglib-1.0 \

contrib/ci/build_and_install_debs.sh

@@ -1,7 +1,9 @@
 #!/bin/bash -e
 
 #build deb packages
-VERSION=`head meson.build | sed "/version :/!d; /meson/d; s/,//; s/'//g;" | awk -F ':' '{print $2}'`
+VERSION=`git describe | sed 's/-/+r/;s/-/+/'`
+[ -z $VERSION ] && VERSION=`head meson.build | grep ' version :' | cut -d \' -f2`
+
 rm -rf build/
 mkdir -p build && pushd build
 ln -s ../* .