CleverCloud: Insert environment variables in declarative config files at deploy

php.json

{
  ...
  "hooks": {
    "postDeploy": "./clevercloud/post-deploy.sh"
  },
  ...
}

post-deploy.sh

#!/bin/bash

# Replace ${VARIABLE} in a file with the corresponding environment variables.
replace_variables () {
  # http://stackoverflow.com/a/5274448/2061091
  perl -p -e 's/\$\{([^}]+)\}/defined $ENV{$1} ? $ENV{$1} : $&/eg; s/\$\{([^}]+)\}//eg' $1 >$2
}

# Move config_local.production.yml to config_local.yml while inserting
# variables environment.
replace_variables app/config/config_local.production.yml app/config-en/config_local.yml