Add argument for amount of entries to request from catalog (fixes #112)

[Sandelinos]

fixes #112

[nmapx]

@andrey-pohilko can it be merged?

[ipavlushin]

@nmapx @Sandelinos These changes might break existing use cases for users. I'd like to keep 10000 as the default value and configure it if necessary. Could you also add a section about entries argument to the Readme?

[Elbandi]

You sould add some pagination for listing images: https://docs.docker.com/registry/spec/api/#pagination

[Elbandi]

ok, here is my tiny solution:

    def list_images(self):
        images = []
        last = ""

        while True:
            result = self.send('/v2/_catalog?n=10&last=' + last)
            if result is None:
                return images
            repos = json.loads(result.text)['repositories']
            if len(repos) == 0:
                break
            images += repos
            last = repos[-1]

        return images

[shrinidhi111]

@nmapx @Sandelinos These changes might break existing use cases for users. I'd like to keep 10000 as the default value and configure it if necessary. Could you also add a section about entries argument to the Readme?

I understand your intention to keep it backward compatible but keeping it at 10k would mean it would break for everyone using the latest registry.

I think @Elbandi suggestion is the way to go