Print the entry point of the images

[rakyll]

When building, print the entry point of the images for users who wants to customize the entry point. Without the entry point printed, it's not clear where the binary is stored without building a debug image.

[imjasonh]

I'm a weak -1 on printing this out during build, but I could be convinced. Aside from added spam in the logs, the bigger reason is that:

[ko] aims to make packaging, pushing, and referencing container images an invisible implementation detail of your Kubernetes deployment, and let you focus on writing code in Go.

If you have to care about what your image's entrypoint is, we've probably done something wrong. There currently isn't a way to change that location within the image at all, and we've sort of resisted adding one.

Would you accept adding a sentence to the README that documents the location of the binary in the image, in case a user happens to care?

[rakyll]

The rationale behind this request is container orchestrators/products require you to provide the entry point if you want to override the default arguments. When I have to provide the binary name with the arguments, I need to know where the binary is.

Would you accept adding a sentence to the README

Yes, documentation is sufficient.

[rakyll]

One more thing. It only takes one debug image to figure it that it's under /ko-app but given the binary name is generated from the package name, I thought that maybe it would be good to print it at ko publish but it's fair to say ko users shouldn't know what's in the image.

[jonjohnsonjr]

I thought that maybe it would be good to print it at ko publish but it's fair to say ko users shouldn't know what's in the image.

I think this could still be reasonable, but I'm a little concerned about spamming logs too much.

It's fairly straightforward (for me) to do:

$ crane config $(ko publish . 2>/dev/null) | jq .config.Entrypoint
[
  "/ko-app/ko"
]

... but I understand that this could be simpler for people who don't care about container tooling that much 😅