[macros] make querying explicit in the main git functions
    
    Querying means that we basically use a cached result if haved
    previously asked git the same question, i.e. tried to pull from
    the git metadata all the merged tags. This is important so that
    we cannot get an inconsistent results renderred into a single spec
    file. This might happen if there is another process writing into
    the repo while a spec file is being renderred.