Created another image for shared scripts.

common/Dockerfile

@@ -0,0 +1,3 @@
+FROM scratch
+
+COPY common.sh /

common/common.sh

@@ -0,0 +1,49 @@
+#!/bin/bash
+
+set -eu
+
+function urldecode { : "${*//+/ }"; echo -e "${_//%/\\x}"; }
+
+function version_from_filename {
+    echo "$1" | sed -r 's#[a-z]+-([0-9_.+]+)-.*#\1#'
+}
+
+function h5ai_query {
+    filename=$(curl -s -S -L -d "action=get&items%5Bhref%5D=%2Fcommunity%2F$1%3A%2F&items%5Bwhat%5D=1" -H \
+                "Accept: application/json" https://download.kopano.io/community/ | jq '.items[].href' | \
+                grep 'Debian_9.0-all\|Debian_9.0-amd64' | sed 's#"##g' | sed "s#/community/$1:/##")
+
+    if [ -z "${filename// }" ]; then
+        echo "unknown component"
+        exit 1
+    fi
+
+    filename=$(urldecode "$filename")
+    echo "$filename"
+}
+
+function dl_and_package_community {
+    # take component as first argument and fallback to core if none given
+    component=${1:-core}
+
+    # query community server by h5ai API
+    filename=$(h5ai_query "$component")
+
+    # download & extract packages
+    curl -s -S -L -o "$filename" https://download.kopano.io/community/"$component":/"${filename}"
+    tar xf "$filename"
+
+    # save buildversion
+    currentVersion=$(version_from_filename "$filename")
+    echo "$component-$currentVersion" >> /kopano/buildversion
+
+    # save disk space
+    rm "$filename"
+
+    mv "${filename%.tar.gz}" "$component"
+
+    # prepare directory to be apt source
+    cd "$component"
+    apt-ftparchive packages . | gzip -9c > Packages.gz
+    cd ".."
+}