docs: add a script to do the tedious work of fetching digests

Add a copy-and-paste-able shell script that one can run to generate
the downloads section of the release notes. This saves the effort
of copy and pasting digests out of the quay.io ui.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

docs/release-process.md

@@ -105,23 +105,51 @@ on GitHub (beyond the sources automatically provided there). Instead we add
 a Downloads section that notes the exact tags and digests that the images can
 be found at on quay.io.
 
-Use the following partial snippet as an example:
-```
-Images built for this release can be obtained from the quay.io image registry.
-
-### samba-server
-* By tag: quay.io/samba.org/samba-server:v0.3
-* By digest: quay.io/samba.org/samba-server@sha256:09c867343af39b237230f94a734eacc8313f2330c7d934994522ced46b740715
-### samba-ad-server
-* By tag: quay.io/samba.org/samba-ad-server:v0.3
-* By digest: quay.io/samba.org/samba-ad-server@sha256:a1d901f44be2af5a516b21e45dbd6ebd2f64500dfbce112886cdce09a5c3cbd5
+The downloads section can be generated using the following shell script:
+```bash
+#!/usr/bin/env bash
+# Requires `skopeo` and `jq` to be installed.
+
+set -e
+
+sk_digest() {
+    skopeo inspect "docker://${1}" | jq -r .Digest
+}
+
+image_info() {
+    curr_img="quay.io/samba.org/${1}:${2}"
+    digest=$(sk_digest "${curr_img}")
+    # strip preN from tag name
+    final_tag="$(echo "$2" | sed 's,pre[0-9]*$,,')"
+    tag_img="quay.io/samba.org/${1}:${final_tag}"
+    dst_img="quay.io/samba.org/${1}@${digest}"
+
+    echo "### $1"
+    echo "* By tag: $tag_img"
+    echo "* By digest: $dst_img"
+    echo ""
+}
+
+wip_tag=$1
+if [ -z "${wip_tag}" ] ; then
+    echo "No tag provided!" >&2
+    exit 1
+fi
+
+echo "## Downloads"
+echo ""
+echo "Images built for this release can be acquired from the quay.io image registry."
+echo ""
+for component in samba-server samba-ad-server samba-client samba-toolbox; do
+    image_info "${component}" "${wip_tag}"
+done
 ```
-... and so on for each image that was pushed earlier
 
-The tag is pretty obvious - it should match the image tag (minus any pre-release
-marker). You can get the digest from the tag using the quay.io UI (do not use
-any local digest hashes). Click on the SHA256 link and then copy the full
-manifest hash using the UI widget that appears.
+It is important that the digest is fetched from qauy.io after it has been
+pushed. Do not use any local digest hashes. You may want to double check the
+values produced by the script with those in the quay.io UI.  Click on the
+SHA256 link and then compare the full manifest hash using the UI widget that
+appears.
 
 Perform a final round of reviews, as needed, for the release notes and then
 publish the release.