Add Dockerfile

[gesellix]

Adds a Dockerfile, which you might use in automated builds on the Dockerhub.

Relates to #126

[SuperSandro2000]

You are missing .git

[gesellix]

Right. It doesn't have any impact on the final image, though. I'll add a fixup later

[SuperSandro2000]

Suggested change

	FROM alpine:3.10 AS builder
	FROM alpine:3.11 AS builder

[SuperSandro2000]

Suggested change

	ENV CGO_ENABLED=0
	ENV CGO_ENABLED=0 GOPATH=/go

[gesellix]

Do we need this?

[SuperSandro2000]

It looks nicer and is easier to convert it to an export ....

[SuperSandro2000]

Suggested change

	RUN apk add --update -t build-deps go git mercurial libc-dev gcc libgcc
	RUN apk add --no-cache -t build-deps go git mercurial libc-dev gcc

You don't update base image packages unless it is needed for a reason.
The removed packages are already pulled in with go.

[SuperSandro2000]

this line is useless

[gesellix]

It's preparation for the next build step

[SuperSandro2000]

Did it get +x somewhere?

[gesellix]

go build handles that one

[SuperSandro2000]

not needed, as you create the user again and the copy can be chowned if needed.

[gesellix]

See above, the user is only created in another build step, here we only apply the minimal change to "create" the user. The user itself is not really necessary, but I consider it a best practice not to run everything as root.

[SuperSandro2000]

If we use FROM scratch we can safely use the root user. There is nothing we can escape to.

[gesellix]

"best practice" refers more to "give future users a chance to make things right by default", so yes, FROM scratch minimizes the attack surface, but what happens if anybody wants to convert the image to a Windows container where we don't have an empty base image? Not that I'd do that, but I prefer to keep those minimal baselines and make people become aware of those aspects.

In fact, I don't actually care if the maintainer of pup thinks the same way, so I consider this PR as simple proposal which can have alternate solutions with more focus on simplicity (see your own Dockerfile you already mentioned).

[SuperSandro2000]

I am pretty sure that a windows variant would have at least 10 more problems cause it is windows and you can't consider everything you might maybe need in the future.

Also this would be a problem for the windows eco system when they only support half of docker.

[gesellix]

Yes, you're right and I fully agree. I hope you got my point, though 😉

[SuperSandro2000]

Also when I try to build this I get:

/pup # go get github.com/ericchiang/pup
# github.com/ericchiang/pup
loadinternal: cannot find runtime/cgo

I would suggest using golang:alpine as a base image as this is the only working workaround I could find for that issue.

[SuperSandro2000]

I quickly wrote this Dockerfile which in my opinion is way nicer, smaller and easier to maintain.

FROM golang:alpine as builder

RUN apk add --no-cache git

RUN go get github.com/ericchiang/pup

WORKDIR $GOPATH/src/github.com/ericchiang/pup

RUN go build -a -ldflags '-s -w -extldflags "-static"' -o /bin/pup

#----------#

FROM scratch

COPY --from=builder /bin/pup /pup

ENTRYPOINT [ "/pup" ]
CMD [ "--help" ]

btw the user switch is not needed as the resulting container is basically empty except pup.

[matthewadams]

Can y'all get this merged and building automatically on hub.docker.com please?