Double slashes in branch names trigger Symfony DI exception on Jenkins

[SvenRtbg]

Our branches use slashes for separation, and Jenkins escaped the slash inside the environment variables BUILD_TAG, JOB_NAME and JOB_BASE_NAME with the sequence %2f. That works with behat if only ONE slash is in the branch name, but Symfony DI will bail out with an exception if we use TWO slashes.

The Selenium2Factory fetches the first two environment variables and puts them into a DI Definition class. Symfony DI sees %variable% inside the string and tries to expand this, but fails because such a variable has not been defined.

With a branch name of test/with/slashes the error produced is

[Symfony\Component\DependencyInjection\Exception\ParameterNotFoundException]
You have requested a non-existent parameter "2fwith".

Our software does not use any Symfony otherwise, this is only related to "behat/mink-extension" version 2.3.1.

(Duplicated as a comment first in #272 (comment))

Symfony DI accepts percent signs in strings and will not try to evaluate them as variables if they are escaped by doubling the percent sign. (See https://github.com/symfony/symfony-standard/issues/1084 for a related issue with a password string).