### Summary Using "manifest-tool" from https://github.com/estesp/manifest-tool, docker multi-arch manifests cannot be created as mounting blobs for cross-repository push fails with http error 401. This issue has also been reported on the manifest-tool project at https://github.com/estesp/manifest-tool/issues/53 ### Steps to reproduce Run the `test-registry.sh` script provided by https://github.com/estesp/manifest-tool against a GitLab Container Registry project. ### Example Project registry.gitlab.com/craiggardener/alpine ### What is the current *bug* behavior? manifest-tool reports: ```` Couldn't mount blobs for cross-repository push: Blob mount failed to url https://registry.gitlab.com/v2/craiggardener/alpine/alpine/blobs/uploads/?from=craiggardener%2Falpine%2Fppc64le_alpine&mount=sha256%3Adaa414b19dcffa0ba7b80abb50a6b31156f1efd7bb1b8cdaeeb848da367afa38: HTTP status 401 ```` GitLab's registry log shows: ```` level=warning msg="error authorizing context: authorization token required" ```` ### What is the expected *correct* behavior? The request should not fail with http error 401. ### Possible fixes Is there any GitLab specific configuration or changes that are required to the authorisation process to make this work?