Retrieves the parameter value for parameter `paramName` from parameter map `map`. In case there is no parameter with the given key contained in parameter map `map``defaultValue` is returned. In case there no such parameter contained in `map` and `defaultValue` is `null` an exception is thrown.
#### Parameters
*`map` - A map containing configuration parameters.
*`paramName` - The key of the parameter which should be looked up.
* optional: `defaultValue` - The value which is returned in case there is no parameter with key `paramName` contained in `map`. If it is not provided the default is `null`.
The value to the parameter to be retrieved, or the default value if the former is `null`, either since there is no such key or the key is associated with value `null`. In case the parameter is not defined or the value for that parameter is `null`and there is no default value an exception is thrown.
Retrieves the git-remote-url and git-branch. The parameters 'GIT_URL' and 'GIT_BRANCH' are retrieved from Jenkins job configuration. If these are not set, the git-url and git-branch are retrieved from the same repository where the Jenkinsfile resides.
*`script` - The script calling the method. Basically the `Jenkinsfile`. It is assumed that the script provides access to the parameters defined when launching the build, especially `GIT_URL` and `GIT_BRANCH`.