GIT PULL: pass a remote to a merge() function

 - make sure to pass remote to merge() function called from pull()
   ammending it imporerly reports "Already up-to-date"
   i.e.: local "HEAD" and "origin/master" differ (after g.fetch)
 -- do g.pull, it will try to merge local "master" to local "HEAD"
    and will say "Already up-to-date"
 -- try explicit 'git.pull("origin","master","origin pull")'
    it will call 'fetch("origin"), then 'merge("master","origin pull")
    without taking remote into account