Docker Support

Which Pulp field(s) needs to support multiple "/"'s? I can't tell if you mean the `repo_id`, the `upstream-name` or something else.

Austin identified this as the limiting factor here:
https://github.com/pulp/pulp_docker/blob/0381e9ecd0a46c05f83bb20d4e584ad7fa81893e/plugins/pulp_docker/plugins/distributors/configuration.py#L317

This should allow for any number of 'slashed' components, while still validating each part:
all(re.match(r"^[a-z0-9-_.]*$", piece) for piece in docker_id.split('/'))

That said, it would (still) be helpful to see docker-docs about what may have change with regard to the validity/invalidity of repo names.

https://github.com/docker/distribution/blob/master/docs/spec/api.md#overview

1. A repository name is broken up into path components. A component of a repository name must be at least one lowercase, alpha-numeric characters, optionally separated by periods, dashes or underscores. More strictly, it must match the regular expression [a-z0-9]+(?:[._-][a-z0-9]+)*.
2. If a repository name has two or more path components, they must be separated by a forward slash ("/").
3. The total length of a repository name, including slashes, must be less than 256 characters.

This may also requires changes to crane. Its v2 endpoints may also assume only one slash.

I'm surprised to see this ability, and I wonder if it gets much use in the wild, but sure enough it does work!

[mhrivnak@dhcp129-40 devel]$ sudo docker tag centos:7 foo/bar/baz
[mhrivnak@dhcp129-40 devel]$ sudo docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
docker.io/centos    7                   980e0e4c79ec        7 weeks ago         196.7 MB
foo/bar/baz         latest              980e0e4c79ec        7 weeks ago         196.7 MB

Given the rules in comment 4, this validation is insufficient:

semyers wrote:

all(re.match(r"^[a-z0-9-_.]*$", piece) for piece in docker_id.split('/'))

I put together this little script along with the regex provided in that comment to check "good" and "bad" docker repo names are correctly classified:

import re

good = ( 
    'this-is-good',
    'this/is/good',
    'this-is/good',
)

bad = ( 
    'bad' * 256,  # 'bad' repeated 256 times, 768 chars total
    '.bad',
    '_bad',
    '-bad',
)

component_re = re.compile('[a-z0-9]+(?:[._-][a-z0-9]+)*')

def validate(name):
    # good names return True, bad names return False
    if len(name) >= 256:
        return False

    for piece in name.split('/'):
        if not re.match(component_re, piece):
            return False

    return True

    # The one-liner version:
    # return len(name) < 256 and all(re.match(component_re, piece) for piece in name.split('/'))

assert all(map(validate, good))
assert not any(map(validate, bad))

The provided regex along with the body of the validate function, appears to correctly validate according to those rules. Add more strings to the "good" and "bad" tuples as desired to prove the validation to your satisfaction.