Add automated version update

Signed-off-by: Knut Ahlers <knut@ahlers.me>

.travis.yml

@@ -0,0 +1,7 @@
+sudo: required
+
+services:
+  - docker
+
+script:
+  - bash update-version.sh

update-version.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+set -e
+set -o pipefail
+
+HOST_OS=$(uname -s)
+
+### ---- ###
+
+echo "Switch back to master"
+git checkout master
+git reset --hard origin/master
+
+### ---- ###
+
+echo "Fetching latest version..."
+LATEST=$(curl -sSLf 'https://latest.luzifer.io/catalog-api/grafana/latest.txt?p=version')
+
+echo "Testing presence of build artifact for ${LATEST}..."
+curl -sSILf https://s3-us-west-2.amazonaws.com/grafana-releases/release/grafana_${LATEST}_amd64.deb
+
+echo "Found version ${LATEST}, patching..."
+sed -i "s/^ENV GRAFANA_VERSION.*$/ENV GRAFANA_VERSION ${LATEST}/" Dockerfile
+
+echo "Checking for changes..."
+git diff --exit-code && exit 0
+
+echo "Testing build..."
+docker build .
+
+echo "Updating repository..."
+git add Dockerfile
+git -c user.name='Travis Automated Update' -c user.email='travis@luzifer.io' \
+  commit -m "Jenkins ${LATEST}"
+git tag ${LATEST}
+
+git push -q https://${GH_USER}:${GH_TOKEN}@github.com/luzifer-docker/grafana.git master --tags