pass the AWS credentials through the Concourse source data

Concourse pipelines dont have a way of setting environment variables,
and this is consistent with how https://github.com/concourse/s3-resource
works.

.env.example

@@ -1,3 +0,0 @@
-# http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-set-up.html#cli-signup
-AWS_ACCESS_KEY_ID=<key>
-AWS_SECRET_ACCESS_KEY=<secret>

.gitignore

@@ -1 +1 @@
-.env
+config.json

README.md

@@ -10,11 +10,8 @@ TODO
 
 Requires Docker.
 
-```bash
-cp .env.example .env
-
-# modify .env
-
-# exclude the `s3://` prefix/protocol for the `bucket`
-./script/run </full/path/to/dir/or/file> <bucket>
-```
+1. Run `cp config.example.json config.json`.
+1. Modify `config.json`.
+    * See [the instructions for getting your AWS credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-set-up.html#cli-signup).
+    * Exclude the `s3://` prefix/protocol for the `bucket`.
+1. Run `./script/run </full/path/to/dir/or/file>`.

assets/out

@@ -20,12 +20,18 @@ fi
 payload=`cat`
 bucket=$(echo "$payload" | jq -r '.source.bucket')
 
+
 echo "Uploading to S3..."
-# credentials are provided via environment variables
+
 # http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-environment
+export AWS_ACCESS_KEY_ID=$(echo "$payload" | jq -r '.source.access_key_id')
+export AWS_SECRET_ACCESS_KEY=$(echo "$payload" | jq -r '.source.secret_access_key')
+
 aws s3 sync $source "s3://$bucket"
+
 echo "...done."
 
+
 # use the current UNIX time as the version
 # https://github.com/concourse/git-resource/blob/6fcfbd4/assets/out#L133-L136
 jq -n "{

config.example.json

@@ -0,0 +1,7 @@
+{
+  "source": {
+    "access_key_id": "",
+    "secret_access_key": "",
+    "bucket": ""
+  }
+}

script/run

@@ -3,19 +3,17 @@
 set -e
 
 source=$1
-bucket=$2
 
-if [ -z "$source" ] || [ -z "$bucket" ]; then
-  echo "usage: $0 </full/path/to/dir/or/file> <bucket>"
+if [ -z "$source" ]; then
+  echo "usage: $0 </full/path/to/dir/or/file>"
   exit 1
 fi
 
+json=$(cat .env.json)
+
 docker build -t 18fgsa/s3-resource-simple .
 
-json="{\"source\": {\"bucket\": \"$bucket\"}}"
-
 echo $json | docker run \
-  --env-file .env \
   -i \
   --rm \
   -v $source:/tmp/input \