oci-image-tool: Drop http.FileSystem?

[wking]

While reading #148, the http.FileSystem section struck me as the wrong approach. “I'd like to validate this content against this JSON Schema” is easy to support generically, and keeping the schemas themselves outside of that tool allows you to use an existing version of the tool to validate new content against new schemas. If you compile the schemas in, you have to rebuild the tool to get access to the new schemas.

For an alternative approach, see the in-flight opencontainers/runtime-spec#490. This approach allows a generic JSON-Schema validator to use whichever schema you point it at. It would be nice to put the schemas up on www.opencontainers.org/schema/…, but even without that you can use the raw GitHub URLs. For oci-image-tool, you'd need a method to convert the detected/configured media type / version to a schema URL, but you already do that for http.FileSystem. The URLs would just get a bit longer, and if we start removing schemas you'd have to add logic to pin to the last image-spec version which carried a schema for your media type.

If this sounds like a reasonable approach, I can work up a PR.

[philips]

I would be fine with making this an optional feature. Requiring network traffic by default doesn't seem like the best default however.

[wking]

On Thu, Jun 16, 2016 at 03:01:46PM -0700, Brandon Philips wrote:

I would be fine with making this an optional feature. Requiring
network traffic by default doesn't seem like the best default
however.

Does Go have defaults for storing associated data (like Python's 1)?
Baking it into the binary seems like “here's my spell checker with a
compiled in snapshot of today's dictionary” (and I hope nobody does
that ;).

[philips]

@wking no, this is the "right" way os doing this for Go. Compiling in the data in a section via a const is the common practice. Not great but that is how it is.

We have a bunch of tools at CoreOS that use this fake filesystem thingie as default and then let people override in "dev" mode.

[s-urbaniak]

Agreeing to all @philips said. I can work on a possibility to look up schema via http/s, or if you @wking would like to do a PR, that'd be fine too.

[wking]

On Fri, Jun 17, 2016 at 06:48:30AM -0700, Sergiusz Urbaniak wrote:

I can work on a possibility to look up schema via http/s…

I'm happy to let you do the work ;).

[philips]

I am going to make this post-v1.0.0 as it feels like a nice to have. Also, labeling as help wanted as it is a fun Go project for someone :)

[philips]

This issue was moved to opencontainers/image-tools#24