I thought it was interesting that, as per the uploader, this was extra footage for the broadcast, an extended beginning directed by Monte Hellman designed to alleviate concerns over the film's violence. Harry Dean Stanton is talking to a stand-in for Clint Eastwood!
According to Wikipedia, this was done for a 1975 TV showing, but other sources indicate it only ran before a 1977 broadcast. Here's what I think about "contextualizing" the violence in the movie with this tacked-on scene:
In that 1977 TV Guide, critic Judith Crist mentions the ABC broadcast of the movie and says it's on its third run. She calls it "the 1964 Italian-German-Spanish rip-off of Akira Kurosawa's Yojimbo. it introduced an obviously waiting world (the film earned millions) to the immutable squint of Clint Eastwood and the flavor of the sadomasochistic blood-red sauce that soaked this spahgetti-spatzle-paella Western. Enough said,"