Merge ~athos-ribeiro/ubuntu-docker-images/+git/prometheus-alertmanager:0.21-20.04-deb-manifest into ~ubuntu-docker-images/ubuntu-docker-images/+git/prometheus-alertmanager:0.21-20.04

[Athos Ribeiro]

Generate manifest to report installed deb packages

* https://bugs.launchpad.net/ubuntu-docker-images/+bug/1953697

[Sergio Durigan Junior (sergiodj)]

LGTM.

review: Approve

diff --git a/Dockerfile b/Dockerfile
index d02a6e7..0ad5b6f 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -21,7 +21,10 @@ RUN set -eux; \
 	DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
 		tzdata; \
 	rm -rf /var/lib/apt/lists/*; \
-	mkdir -p /alertmanager
+	mkdir -p /alertmanager; \
+	mkdir -p /usr/share/rocks; \
+# create deb manifest
+	(echo "# os-release" && cat /etc/os-release && echo "# dpkg-query" && dpkg-query -f '${db:Status-Abbrev},${binary:Package},${Version},${source:Package},${Source:Version}\n' -W) > /usr/share/rocks/dpkg.query
 
 COPY --from=snap-installer /snap/prometheus-alertmanager/bin/alertmanager /usr/bin/alertmanager
 COPY --from=snap-installer /snap/prometheus-alertmanager/bin/amtool /usr/bin/amtool