Update used Xcode image for Travis automatically

update-travis.sh

#!/bin/sh

function available_versions() {
	curl -s 'https://docs.travis-ci.com/user/languages/objective-c/'| \
		grep 'osx_image: '|sed -e 's_.*<code>\(osx\_image.*\)</code>.*_\1_'|sort|uniq	
}

function latest_version {
	available_versions|tail -n 1
}

function used_version {
	cat .travis.yml|grep 'osx_image: '
}

set -e

if [ ! -f ".travis.yml" ]
then
	echo "No Travis configuration found."
	exit 1
fi

if [ -n "`git status -s`" ]
then
	echo "Git status is not clean."
	exit 1
fi

LATEST="`latest_version`"
LATEST_IMAGE=`echo "$LATEST"|cut -d' ' -f2-`
USED="`used_version`"

if [ "$LATEST" != "$USED" ]
then
	echo "Used Xcode image is outdated."

	branch="update-travis-to-$LATEST_IMAGE"
	message="Update Travis to $LATEST_IMAGE"

	git checkout -b "$branch"
	sed -i '' -e "s/^$USED$/$LATEST/" .travis.yml
	git add .travis.yml
	git commit -m "$message"
	git push -u origin "$branch"

	url=`hub pull-request -m "$message"`
	open $url

	git checkout master
	git branch -D "$branch"
fi