[ci] Set the value of 'general.revisions_enabled' only if given (#6492)
[ci] Set the value of 'general.revisions_enabled' only if given (#6492)

* only set revisions value if explicit (user input over environment)

* use 'revisions_enabled' branch from CI repo

* create folder if not exists

* function not available in older pythons

* using 'master' it should work the same way

conan-io/conan,conan-io/conan,conan-io/conan