title: Avoiding and renaming .x and .y columns when merging or joining in r
body: <p>Often I go about joining two dataframes together that have the same name.  Is there a way to do this within the join-step so that I don't end up with a .x and a .y column?  So the names might be 'original_mpg', and 'new_mpg'?</p>
  
  <pre><code>  library(dplyr)
    left_join(mtcars, mtcars[,c("mpg",'cyl')], by=c("cyl"))
    names(mtcars) #ugh
  </code></pre>