Cache bundle results on Travis to S3

Hopefully speeds up builds

.travis.yml

@@ -1,6 +1,7 @@
 before_install:
  - sudo apt-get update -qq
  - sudo apt-get install -qq tmux zsh git
+install: script/cached-bundle install --deployment
 script: script/test
 language: ruby
 rvm:
@@ -13,3 +14,8 @@ notifications:
     recipients:
       - mislav.marohnic@gmail.com
     on_success: never
+env:
+  global:
+    - AMAZON_S3_BUCKET=ci-cache
+    - AMAZON_ACCESS_KEY_ID=AKIAJQCVTDEWQHRPBPGQ
+    - secure: "XAZv5xyNjWt7F9hG0MZhDANVJ5h/ajEZvfJOEIZRQlE3X5x6oVgI8blLh/MmlRSF0kIyLckcn6t2ccjSOvwN2hca5bwZSjIqoKbJyNe2cmkxfi2432vEOu3Ve6PT5hZWX4R5RgT+xWyMjIJcdF3gUMP7ErXl64aEncBzeW6OoXM="

script/cached-bundle

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Usage: cached-bundle install --deployment
+#
+# After running `bundle`, caches the `vendor/bundle` directory to S3.
+# On the next run, restores the cached directory before running `bundle`.
+#
+# Requirements:
+# - TRAVIS_REPO_SLUG
+# - TRAVIS_RUBY_VERSION
+# - AMAZON_S3_BUCKET
+# - script/s3-put
+
+set -e
+
+compute_md5() {
+  local output="$(openssl md5)"
+  echo "${output##* }"
+}
+
+download() {
+  curl --tcp-nodelay -qsfL "$1" -o "$2"
+}
+
+bundle_path="vendor/bundle"
+gemfile_hash="$(compute_md5 <"${BUNDLE_GEMFILE:-Gemfile}.lock")"
+cache_name="${TRAVIS_RUBY_VERSION}-${gemfile_hash}.tgz"
+fetch_url="http://${AMAZON_S3_BUCKET}.s3.amazonaws.com/${TRAVIS_REPO_SLUG}/${cache_name}"
+
+if download "$fetch_url" "$cache_name"; then
+  echo "Reusing cached bundle ${cache_name}"
+  tar xzf "$cache_name"
+fi
+
+bundle "$@"
+
+if [ ! -f "$cache_name" ]; then
+  echo "Caching \`${bundle_path}' to S3"
+  tar czf "$cache_name" "$bundle_path"
+  script/s3-put "$cache_name" "${AMAZON_S3_BUCKET}:${TRAVIS_REPO_SLUG}/${cache_name}"
+fi

script/s3-put

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+# Usage: s3-put <FILE> <S3_BUCKET>[:<PATH>] [<CONTENT_TYPE>]
+#
+# Uploads a file to the Amazon S3 service.
+#
+# Depends on AWS credentials being set via env:
+# - AMAZON_ACCESS_KEY_ID
+# - AMAZON_SECRET_ACCESS_KEY
+#
+# Outputs the URL of the newly uploaded file.
+set -e
+
+authorization() {
+  local signature="$(string_to_sign | hmac_sha1 | base64)"
+  echo "AWS ${AMAZON_ACCESS_KEY_ID?}:${signature}"
+}
+
+hmac_sha1() {
+  openssl dgst -binary -sha1 -hmac "${AMAZON_SECRET_ACCESS_KEY?}"
+}
+
+base64() {
+  openssl enc -base64
+}
+
+bin_md5() {
+  openssl dgst -binary -md5
+}
+
+string_to_sign() {
+  echo "$http_method"
+  echo "$content_md5"
+  echo "$content_type"
+  echo "$date"
+  echo "x-amz-acl:$acl"
+  printf "/$bucket/$remote_path"
+}
+
+date_string() {
+  LC_TIME=C date "+%a, %d %h %Y %T %z"
+}
+
+file="$1"
+bucket="${2%%:*}"
+remote_path="${2#*:}"
+content_type="$3"
+
+if [ -z "$remote_path" ] || [ "$remote_path" = "$bucket" ]; then
+  remote_path="${file##*/}"
+fi
+
+http_method=PUT
+acl="public-read"
+content_md5="$(bin_md5 < "$file" | base64)"
+date="$(date_string)"
+
+url="https://$bucket.s3.amazonaws.com/$remote_path"
+
+curl -qsSf -T "$file" \
+  -H "Authorization: $(authorization)" \
+  -H "x-amz-acl: $acl" \
+  -H "Date: $date" \
+  -H "Content-MD5: $content_md5" \
+  -H "Content-Type: $content_type" \
+  "$url"
+
+echo "$url"