Update engine infructure

* Added engine specification
* Switched from generic date built to engine/lint version pair for image
  rebuild trigger. The version is stored in the engine spec under
  `version` key. It's format is
  `<engine version>/<lint master head sha1>`.
  * Bump engine version whenever the code in this repository changes.
  * Run `make update` to update the lint version part.
* Switched to newer Go version.

Author: pointlessone

DATE_BUILT

@@ -1,23 +1,24 @@
-FROM alpine:3.4
+FROM alpine:edge
 
-MAINTAINER Code Climate <hello@codeclimate.com>
+LABEL maintainer="Code Climate <hello@codeclimate.com>"
+
+RUN adduser -u 9000 -D app
 
 WORKDIR /usr/src/app
+
+COPY engine.json /engine.json
 COPY codeclimate-golint.go /usr/src/app/codeclimate-golint.go
-COPY DATE_BUILT /usr/src/app/DATE_BUILT
 
-RUN apk --update add go git && \
+RUN apk add --no-cache --virtual .dev-deps musl-dev go git && \
   export GOPATH=/tmp/go GOBIN=/usr/local/bin && \
-  go get -d . && \
+  go get -d -t -v . && \
+  export LIBRARY_PATH=/usr/lib32:$LIBRARY_PATH && \
   go install codeclimate-golint.go && \
-  apk del go git && \
-  rm -rf "$GOPATH" && \
-  rm /var/cache/apk/*
+  apk del .dev-deps && \
+  rm -rf "$GOPATH"
 
+USER app
 WORKDIR /code
 VOLUME /code
 
-RUN adduser -u 9000 -D app
-USER app
-
 CMD ["/usr/local/bin/codeclimate-golint"]

Dockerfile

@@ -1,6 +1,14 @@
-.PHONY: image
+.PHONY: update image
 
 IMAGE_NAME ?= codeclimate/codeclimate-golint
 
-image:
+update:
+	docker run \
+	  --rm --interactive \
+	  -v $(PWD)/engine.json:/engine.json \
+	  -v $(PWD)/bin/update:/usr/local/bin/update \
+	  alpine:edge \
+	  /usr/local/bin/update
+
+image: update
 	docker build --rm -t $(IMAGE_NAME) .

Makefile

@@ -28,14 +28,20 @@ engines:
 ### Building
 
 ```console
-docker build -t codeclimate/codeclimate-golint .
+make image
 ```
 
 ### Updating
 
 `golint` doesn't version releases, so in order to get the latest version & force
-a new docker image build, we have a `DATE_BUILT` file: to force an update of
-golint, run `date > DATE_BUILT` locally & then rebuild the docker image.
+a new docker image build, we have to update the `engine.json` file.
+
+```console
+make update
+```
+
+This will update the engine version with the latest `golint` version. After that
+rebuild the image as usually.
 
 ### Need help?
 

README.md

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+set -e
+
+apk add --no-cache curl jq
+head_sha=$(
+  curl -s $(
+      curl -s "https://api.github.com/repos/golang/lint/git/refs/heads/master" |
+      jq -r .object.url
+  ) |
+  jq -r .sha
+)
+full_version="$(jq -r .version /engine.json | cut -d / -f 1)/${head_sha}"
+jq ".version=\"${full_version}\"" /engine.json > /tmp/engine.json &&
+  cat /tmp/engine.json > /engine.json

bin/update

@@ -0,0 +1,13 @@
+{
+  "name": "golint",
+  "description": "Golint is a linter for Go source code.",
+  "maintainer": {
+    "name": "Code Climate",
+    "email": "hello@codeclimate.com"
+  },
+  "languages": [
+    "Go"
+  ],
+  "version": "1.0.0/6aaf7c34af0f4c36a57e0c429bace4d706d8e931",
+  "spec_version": "0.3.1"
+}