git-gui: Show original filename in blame tooltip

If we have two commits right next to each other in the final
file and they were kept as different blocks in the leftmost
column then its probably because the original filename was
different.  To help the user know where they are digging into
when they click on that link we now show the original file in
the tooltip, but to save space we do so only if the original
file is not the same as the file we are currently viewing.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

lib/blame.tcl

@@ -805,6 +805,13 @@ method _open_tooltip {cur_w} {
 $author_name $author_email  $author_time
 $summary"
 
+	set file $line_file($lno)
+	if {$file ne $path} {
+		append tooltip_text "
+
+Original File: $file"
+	}
+
 	if {$tooltip_wm ne "$cur_w.tooltip"} {
 		_hide_tooltip $this