Rewrite Introduction section of specification

[stevvooe]

Signed-off-by: Stephen J Day stephen.day@docker.com

[stevvooe]

@icecrime @dmcgowan @jlhawn @dmp42 @BrianBland @AndreyKostov

[icecrime]

I'm a little confused by this:

The specification covers the operation of version 2 of this API

And later:

While the V2 registry protocol is usable, there are several problems with the architecture that have led to this new version

[BrianBland]

If you see above from the first line, this was originally labeled "V2.1".

We still need some way of clearing the ambiguity about this not being the same as the "V2" API that was originally defined in docker/docker-registry#612

[stevvooe]

This sentence should read "While the V1 registry protocol is usable".

[BrianBland]

It won't let me comment on the unchanged part, but we should specify that (bolded the addition) "A component of a repository name must be at least two lowercase alphanumeric characters...".

Additionally, the regular expression can be changed to ^[a-z0-9]+([._-]?[a-z0-9]+)+$, which removes the need for the clarification about 2+ character length.

[stevvooe]

Additionally, the regular expression can be changed to ^[a-z0-9]+([._-]?[a-z0-9]+)+$, which removes the need for the clarification about 2+ character length.

@BrianBland I've specified this in prose purposely to avoid the confusion we had about regular expressions before.

[dmp42]

LGTM

[icecrime]

LGTM