ExecManifest.scala copies the docker/distribution image-reference grammar without attribution #266

build/openwhisk/common/scala/src/main/scala/org/apache/openwhisk/core/entity/ExecManifest.scala (vendored from Apache OpenWhisk, shipped in the 0.9.0-incubating-RC7 source release) contains the Docker image-reference grammar copied from docker/distribution:

    // docker image name grammar, taken from: https://github.com/docker/distribution/blob/master/reference/reference.go
    //
    // Grammar
    //
    // reference                       := name [ ":" tag ] [ "@" digest ]
    // name                            := [domain '/'] path-component ['/' path-component]*
    // domain                          := domain-component ['.' domain-component]* [':' port-number]
    // domain-component                := /([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])/
    // ...
    // digest-hex                      := /[0-9a-fA-F]{32,}/ ; At least 128 bit digest value

The 18-line grammar block is copied verbatim from the package comment of reference/reference.go in docker/distribution (now maintained as distribution/reference), and the parser below it (ImageName) implements that grammar. docker/distribution is licensed under the Apache License 2.0.

There is no licence conflict, but the copied text is not attributed: the file only carries the ASF header, and the top-level LICENSE does not mention docker/distribution. The existing comment gives the source URL, which is a good start but not a licence attribution. The link is also broken: it returns a 404. docker/distribution was renamed to distribution/distribution, its default branch changed from master to main, and the reference package was moved out into its own repository, distribution/reference. GitHub redirects the old URL to distribution/distribution on main, where reference/reference.go no longer exists.

Suggested fix, either:

1. Add a LICENSE entry noting that the image-name grammar in this file is taken from docker/distribution reference/reference.go (Apache-2.0), and update the link to a pinned tag, e.g. https://github.com/distribution/distribution/blob/v2.7.1/reference/reference.go; or
2. Replace the copied grammar with a short description in our own words plus the pinned link.

The same code is in upstream Apache OpenWhisk. Related: #260.