git-gui: scroll down to default selection for push dialog

If the list of remote/local branches is very long its inconvenient
to scroll down and find the selected branch. This patch makes the
widget automatically scroll down so its shown on the top.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>

lib/transport.tcl

@@ -123,6 +123,7 @@ proc do_push_anywhere {} {
 		$w.source.l insert end $h
 		if {$h eq $current_branch} {
 			$w.source.l select set end
+			$w.source.l yview end
 		}
 	}
 	pack $w.source.l -side left -fill both -expand 1