sync-tags.sh

#!/usr/bin/env bash
# utility for syncing docker images across repos, or even registries
# depends on regclient. installation guide:  https://github.com/regclient/regclient/blob/main/docs/install.md
# edit IMAGE_A and IMAGE_B below to whatever you want

# if the tags exist on both sides, but differ, A is the authoritative source (B will be overwritten)
IMAGE_A="ghcr.io/wukko/cobalt"
IMAGE_B="ghcr.io/justusecobalt/cobalt"

set -eu -o pipefail
ALL_TAGS=$(sort -Vru < <(printf '%s\n%s\n' "$(regctl tag ls $IMAGE_A)" "$(regctl tag ls $IMAGE_B)"))

N=8
for tag in $ALL_TAGS; do
    SOURCE="$IMAGE_A:$tag"
    DEST="$IMAGE_B:$tag"

    (
	    echo "checking $SOURCE <-> $DEST"
	    DIFF=$(regctl manifest diff "$SOURCE" "$DEST" 2>/dev/null || echo 404)
	    if [ "$DIFF" != "" ]; then
	        regctl image copy "$SOURCE" "$DEST" || true
		sleep 3
	        regctl image copy "$DEST" "$SOURCE" || true
	    fi
    ) &

    if [[ $(jobs -r -p | wc -l) -ge $N ]]; then
        wait -n
    fi
done