copyGitFile: Create 1.7 from 1.6
copyGitFile/1.7: Add option in metadata.xml
copyGitFile/1.7: Add the code to call rudder_copy_from with purge to true or not
copyGitFile/1.7: Set false as the default value
copyGitFile/1.7: constraint must be applied on value not label
copyGitFile: Rename to 2.1 to respect technique versioning - http://www.rudder-project.org/foswiki/Development/TechniqueVersioning