Add additional output formats (tarball and layout)

[jonjohnsonjr]

Fixes #128
Closes #95

This is staged in a few commits that should be easy to review independently:

• Create a MultiPublisher
• Add publish.{Tarball,Layout}Publisher
• Consolidate publisher options
• Add flags for tarball/layout publishers

[jonjohnsonjr]

@bioball @josephlewis42 @jbarrick-mesosphere

Would this work for all of your needs?

[bioball]

Awesome!! Although, I just tried it, and it doesn't seem like all the images within ko resolve are getting added to the tarball. This is what I see when building https://github.com/tektoncd/pipeline:

$ ko resolve --tarball=output.tar -f config > release.yaml
$ cat output.tar | docker load
# => Loaded image: localhost:5000/mypipelineimages/controller-10a3e32792f33651396d02b6855a6e36:latest

However, I'd expect to find a lot more images in there. These are the images that got built and inserted into release.yaml:

localhost:5000/mypipelineimages/pullrequest-init-4e60f6acf9725cba4c9b0c81d0ba89b8@sha256:1ca483f81029306cfb5aec449a8f8a33f767f7eaa3c91f3709046aa04c5ee9e3
localhost:5000/mypipelineimages/gcs-fetcher-029518c065a5d298216f115c6595f133@sha256:a15e480c72aa283ce25bd1fbee92a6eff9ef3b01fcb05c36724724d67b4ddbce
localhost:5000/mypipelineimages/creds-init-c761f275af7b3d8bea9d50cc6cb0106f@sha256:b3fee8be2abeca4068afeabc13fdcb5239bf4736d2798ecb51b9f7d1e76cecb1
localhost:5000/mypipelineimages/imagedigestexporter-6e7c518e6125f31761ebe0b96cc63971@sha256:4c4240a16e935c8fd4cc6388c33b452ba09c4c14eb4fd8f7c407856e90d9a233
localhost:5000/mypipelineimages/entrypoint-bff0a22da108bc2f16c818c97641a296@sha256:5ef95def223c30b9e88a370512956b09a7a816695b83e3f30d40c1e6a54bb895
localhost:5000/mypipelineimages/kubeconfigwriter-3d37fea0b053ea82d66b7c0bae03dcb0@sha256:29acbfe6b4bc133f58e0664437926ca0bd7a13ce98d5b409c8cf12306cf8fd0b
localhost:5000/mypipelineimages/webhook-d4749e605405422fd87700164e31b2d1@sha256:e2e114e1be7ef2e8ede9e84241b6654287faea1bbdff80f00574b2f4466d3acd
localhost:5000/mypipelineimages/git-init-4874978a9786b6625dd8b6ef2a21aa70@sha256:51f215e953750b51a2b059177b3c285a8baefb8862f29a5e883f6af667ed10e0
localhost:5000/mypipelineimages/controller-10a3e32792f33651396d02b6855a6e36@sha256:e0060a3fde69273eccda239c3c1c174f4272a453c8cb2c764f91be7645fe8

[jonjohnsonjr]

doesn't seem like all the images within ko resolve are getting added to the tarball

Ahh yeah I forgot to go back and fix this, thanks. There's not an easy way to append an image to a tarball right now (since the interface supports streaming writes). Hacked a workaround in to just buffer images until the end and write them out in a Close().

Try it now 😄

[bioball]

Looks like it works!

[bioball]

LGTM for the tarball stuff

[josephlewis42]

This looks like it will fit our purposes nicely!