This script can be used to copy all docker images from one GitLab-project to another. It was created because in GitLab it's not possible to move projects that contain docker images.

copy_images.sh

#!/usr/bin/env bash

# This script can be used to copy all docker images from one GitLab-project to another. 
# It was created because in GitLab it's not possible to move projects that contain docker images.
#
# Related issue: https://gitlab.com/gitlab-org/gitlab/-/issues/18383
#
# Author: Daniel Estermann <estermad@apache.org>
# Thanks to komar <komar@core.org.ua> for his brilliant support

ME=$(basename "$0")
DEPENDS="docker curl jq tac"

die() {
  if [[ "$*" && -t 2 ]]; then
    printf "\e[31;1m%s\e[0m\n" "$*" >&2
  else
    printf "%s\n" "$*" >&2
  fi
  exit 1
}

usage() {
  cat <<- EOM
		Usage: $ME <gitlab-server> <path-to-project> <new-path-to-project>

		Example: $ME gitlab.com johndoe/foo johndoe/bar
	EOM
  exit 1
}

[[ ${GITLAB_TOKEN} ]] || die "Please provide an access token via the environment variable GITLAB_TOKEN"

for CMD in $DEPENDS; do
  command -v $CMD >/dev/null 2>&1 || die "This script requires $CMD but it's not installed. Aborting."
done

docker ps >/dev/null 2>&1 || die "This script requires docker but its engine is unreachable. Aborting."

[[ ${1} && ${2} && ${3} ]] || usage

PROJECT_NS=${2//\//%2F}

REPOSITORY_IDS=$(curl -s -H "PRIVATE-TOKEN:${GITLAB_TOKEN}" \
                   "https://$1/api/v4/projects/${PROJECT_NS}/registry/repositories/" |
                     jq -r '.[].id' 2>/dev/null)
[[ ${REPOSITORY_IDS} ]] || die "$1/$2 has no docker images"

TMPFILE=$(mktemp -u /tmp/$ME.XXXXXX)

for REPOSITORY_ID in $REPOSITORY_IDS; do

  TAGS_URL="https://$1/api/v4/projects/${PROJECT_NS}/registry/repositories/${REPOSITORY_ID}/tags?per_page=100"
  
  TOTAL_PAGES=$(curl -sI -X HEAD -H "PRIVATE-TOKEN:${GITLAB_TOKEN}" ${TAGS_URL} |
                    sed -nE 's/X-Total-Pages:[[:space:]]*([^'$'\r'']*)'$'\r''?/\1/ip')
  [[ $TOTAL_PAGES =~ ^[0-9]+$ ]] || die "Error getting total page number using HTTP HEAD on $TAGS_URL (got $TOTAL_PAGES)"

  for PAGE in $(seq 1 $TOTAL_PAGES); do
    curl -s -H "PRIVATE-TOKEN:${GITLAB_TOKEN}" "${TAGS_URL}&page=${PAGE}" |
        jq -r '.[].location'
  done |
    sed -E "s#(.*)#docker pull \1 \&\& docker tag \1 \1#g
            s#(.*)($2)(.*:.*)#\1$3\3#i" |
      tee -a $TMPFILE

done

cat << EOM >> $TMPFILE
while true; do
    read -p "Do you want to push the images now? [Y/n] " yn
    case \${yn:-Y} in
        [Yy]* ) break;;
        * ) echo "Abort."; exit;;
    esac
done
EOM

tac $TMPFILE | sed '1,7d' | tac |
  sed -E "s#.* (.*)#docker push \1#" |
    tee -a $TMPFILE

[[ -f $TMPFILE ]] &&
  chmod +x $TMPFILE &&
    echo "You can now review the generated script in stdout or in $TMPFILE and if it looks fine for you just execute it." ||
      die "Something went wrong, sorry :("

@Smasherr This is the output:

$ ./copy_images.sh <our_server> <original_repo> jan.wendler/temp
++ basename ./copy_images.sh
+ ME=copy_images.sh
+ DEPENDS='docker curl jq tac'
+ [[ -n <Token> ]]
+ for CMD in $DEPENDS
+ command -v docker
+ for CMD in $DEPENDS
+ command -v curl
+ for CMD in $DEPENDS
+ command -v jq
+ for CMD in $DEPENDS
+ command -v tac
+ docker ps
+ [[ -n <our_server> ]]
+ [[ -n <original_repo> ]]
+ [[ -n jan.wendler/temp ]]
+ PROJECT_NS=<original_repo_%2F>
++ curl -s -H PRIVATE-TOKEN:<Token> https://<our_server>/api/v4/projects/<original_repo_%2F>/registry/repositories/
++ jq -r '.[].id'
+ REPOSITORY_IDS=1702
+ [[ -n 1702 ]]
++ mktemp -u /tmp/copy_images.sh.XXXXXX
+ TMPFILE=/tmp/copy_images.sh.AIoZz4
+ for REPOSITORY_ID in $REPOSITORY_IDS
+ TAGS_URL='https://<our_server>/api/v4/projects/<original_repo_%2F>/registry/repositories/1702/tags?per_page=100'
++ curl -sI -X HEAD -H PRIVATE-TOKEN:<Token> 'https://<our_server>/api/v4/projects/<original_repo_%2F>/registry/repositories/1702/tags?per_page=100'
++ sed -nE 's/X-Total-Pages:[[:space:]]*([^]*)?/\1/ip'
sed: -e expression #1, char 41: unterminated `s' command
+ TOTAL_PAGES=
+ [[ '' =~ ^[0-9]+$ ]]
+ die 'Error getting total page number using HTTP HEAD on https://<our_server>/api/v4/projects/<original_repo_%2F>/registry/repositories/1702/tags?per_page=100 (got )'
+ [[ -n Error getting total page number using HTTP HEAD on https://<our_server>/api/v4/projects/<original_repo_%2F>/registry/repositories/1702/tags?per_page=100 (got ) ]]
+ [[ -t 2 ]]
+ printf '\e[31;1m%s\e[0m\n' 'Error getting total page number using HTTP HEAD on https://<our_server>/api/v4/projects/<original_repo_%2F>/registry/repositories/1702/tags?per_page=100 (got )'
Error getting total page number using HTTP HEAD on https://<our_server>/api/v4/projects/<original_repo_%2F>/registry/repositories/1702/tags?per_page=100 (got )
+ exit 1

I'm working on Windows 10 with an elevated gitbash console. I hope this helps : )