Move docs to ko.build (#749)

* Move docs to ko.build

* rm ko_deps.md

* remove trailing whitespace

* add go-import meta tag

* update mkdocs.yml

* update mkdocs.yml

* remove duplicate main.html

* update go.sum

docs/advanced/migrating-from-dockerfile.md

@@ -0,0 +1,64 @@
+# Migrating from Dockerfile
+
+If your `Dockerfile` looks like either of the examples in the [official tutorial for writing a Dockerfile to containerize a Go application](https://docs.docker.com/language/golang/build-images/), you can easily migrate to use `ko` instead.
+
+Let's review the best practice multi-stage Dockerfile in that tutorial first:
+
+```plaintext
+# syntax=docker/dockerfile:1
+
+##
+## Build
+##
+FROM golang:1.16-buster AS build
+
+WORKDIR /app
+
+COPY go.mod ./
+COPY go.sum ./
+RUN go mod download
+
+COPY *.go ./
+
+RUN go build -o /docker-gs-ping
+
+##
+## Deploy
+##
+FROM gcr.io/distroless/base-debian10
+
+WORKDIR /
+
+COPY --from=build /docker-gs-ping /docker-gs-ping
+
+EXPOSE 8080
+
+USER nonroot:nonroot
+
+ENTRYPOINT ["/docker-gs-ping"]
+```
+
+This `Dockerfile`:
+
+1. pulls the `golang:1.16` image
+1. `COPY`s your local source into the container environment (`COPY`ing `go.mod` and `go.sum` first and running `go mod download`, to cache dependencies in the container environment)
+1. `RUN`s `go build` on your source, inside the container, to produce an executable
+1. `COPY`s the executable built in the previous step into a new image, on top of a minimal [distroless](https://github.com/GoogleContainerTools/distroless) base image.
+
+The result is a Go application built on a minimal base image, with an optimally cached build sequence.
+
+After running `docker build` on this `Dockerfile`, don't forget to push that image to the registry so you can deploy it.
+
+---
+
+## Migrating to `ko`
+
+If your Go source is laid out as described in the tutorial, and you've [installed](./../install) and [set up your environment](./../get-started), you can simply run `ko build ./` to build and push the container image to your registry.
+
+You're done. You can delete your `Dockerfile` and uninstall `docker`.
+
+`ko` takes advantage of your local [Go build cache](./../features/build-cache) without needing to be told to, and it sets the `ENTRYPOINT` and uses a nonroot distroless base image by default.
+
+To build a multi-arch image, simply add `--platform=all`.
+Compare this to the [equivalent Docker instructions](https://docs.docker.com/desktop/multi-arch/).
+