Merge branch 'rr/complete-difftool-fixup'

"git difftool" can take both revs to be compared and pathspecs.
"git show" takes revs, revs:path and pathspecs.

* rr/complete-difftool-fixup:
  completion: show can take both revlist and paths
  completion: difftool takes both revs and files

contrib/completion/git-completion.bash

@@ -1211,7 +1211,7 @@ _git_difftool ()
 		return
 		;;
 	esac
-	__git_complete_file
+	__git_complete_revlist_file
 }
 
 __git_fetch_options="
@@ -2277,7 +2277,7 @@ _git_show ()
 		return
 		;;
 	esac
-	__git_complete_file
+	__git_complete_revlist_file
 }
 
 _git_show_branch ()