ref file name identical to tag

[xiekeyang]

The ref file name should be identical to tag it presents, from implementation side. And this had better to be amended in Implementor's Note section.

Signed-off-by: xiekeyang xiekeyang@huawei.com

[wking]

On Mon, Sep 19, 2016 at 03:50:21AM -0700, xiekeyang wrote:

The ref file name should be identical to tag it presents, from
implementation side.

This is not true. See moby/moby#25779, which currently defaults
to “have the ref match the tag” but lets you override that default to
use any tag you like. If you require the ref to match the tag,
storing multiple images in a single oci-layout becomes confusing
(always) or impossible (when both images use the same tag).

[xiekeyang]

@wking

If you require the ref to match the tag,
storing multiple images in a single oci-layout becomes confusing
(always) or impossible (when both images use the same tag).

Here I'm unclear to both images use the same tag. Can you present a example?
Normally the layout is like:

.
├── blobs
│   └── sha256
│       ├── 2b8fd9751c4c0f5dd266fcae00707e67a2545ef34f9a29354585f93dac906749
│       ├── 8ddc19f16526912237dd8af81971d5e4dd0587907234be2b83e249518d5b673f
│       └── cf51ed98e7bdfd2a0dcd8dba91947e409b015a7582d0ac4703cf6338021e83b9
└── refs
    ├── latest
    └── v2.0

What is the layout for same tag case? Do you mean a layout includes images: hello-world:latest and busybox:latest ?

[wking]

On Tue, Sep 20, 2016 at 02:09:19AM -0700, xiekeyang wrote:

What is the layout for same tag case? Do you mean a layout includes
images: hello-world:latest and busybox:latest ?

Yeah. The example @stevvooe gives in moby/moby#25779 is to have
refs for both redis:latest and alpine:latest in the same image-layout
tarball.

[stevvooe]

@wking I think we can add language to this effect that makes the common ref-tag mapping clear but allows for other mappings.

[wking]

On Tue, Sep 20, 2016 at 12:06:28PM -0700, Stephen Day wrote:

@wking I think we can add language to this effect that makes the
common ref-tag mapping clear but allows for other mappings.

I think the “In the wild…” line below already makes this use case
pretty clear, and would rather avoid “are identical to” for clarifying
a common use case when tags/refs are not identical in general. But
I'm open to other rewordings of this line. How about:

A common use case is to use “tag” names as refs.

which repaces the current “representing” with “use… as”.

[xiekeyang]

@wking @stevvooe
Fix it. How about new languages?
with using "tag" as ref file names is just A common use case.
which is(not MUST) identical to ref file names is in the case of you often see.
Consumers can be clear how to use it, and regard it as common case.

[wking]

This still seems a bit awkward to me. This this suggestion is too brief, how about leaving the current there lines as they stand in master to convey (by sentence):

1. Refs are often used for tags.
2. Images are often tagged by version or build.
3. Tags look like {examples}.

Then add an additional sentence to cover your additional point:

Those tags will often be represented in an image-layout repository with matching refs like "v1.0.0-vendor.0”, “2.0.0-debug”, etc.

[xiekeyang]

Updated.

[wking]

14597a3 looks good to me.

[xiekeyang]

PTAL.

[vbatts]

LGTM

[stevvooe]

LGTM