new: [mongo] provide ``upstream-versions`` hook

mongo/hooks/upstream-versions

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+## List upstream available versions in reverse chronological order
+##
+## These versions information will be the input for the version information
+## usually used by the build process.
+## A external query of upstream sources will be done.
+##
+
+## This script is launched by ``charm upstream-versions`` and will receive these env variables
+##
+##
+##  VERSION_LIMIT   ## limit number of version to read
+##
+##
+## The script CWD will be the root of the charm directory
+##
+
+DOCKER_IMAGE_NAME=mongo
+
+semver:normalize() {
+    local upstream_version="$1"
+    echo "$upstream_version"
+}
+
+
+upstream:list() {
+    local limit=${1:-5}
+    docker-tags-fetch "$DOCKER_IMAGE_NAME" -l "${limit}" -f "^[0-9]+\.[0-9]+\.[0-9]+$" |
+        sort -rV
+}
+
+
+while read -r "upstream_version"; do
+    printf "%s %s\n" "$(semver:normalize "${upstream_version}")" "$upstream_version"
+done < <(upstream:list "${VERSION_LIMIT}")