gitk: Simplify file filtering

git diff is perfectly able to do this with '-- files', no need for
manual filtering.  This makes gettreediffs consistent with getblobdiffs.
Signed-off-by: NFelipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

gitk

@@ -7618,9 +7618,13 @@ proc diffcmd {ids flags} {
 }
 
 proc gettreediffs {ids} {
-    global treediff treepending
+    global treediff treepending limitdiffs vfilelimit curview
 
-    if {[catch {set gdtf [open [diffcmd $ids {--no-commit-id}] r]}]} return
+    set cmd [diffcmd $ids {--no-commit-id}]
+    if {$limitdiffs && $vfilelimit($curview) ne {}} {
+	    set cmd [concat $cmd -- $vfilelimit($curview)]
+    }
+    if {[catch {set gdtf [open $cmd r]}]} return
 
     set treepending $ids
     set treediff {}
@@ -7664,17 +7668,7 @@ proc gettreediffline {gdtf ids} {
 	return [expr {$nr >= $max? 2: 1}]
     }
     close $gdtf
-    if {$limitdiffs && $vfilelimit($curview) ne {}} {
-	set flist {}
-	foreach f $treediff {
-	    if {[path_filter $vfilelimit($curview) $f]} {
-		lappend flist $f
-	    }
-	}
-	set treediffs($ids) $flist
-    } else {
-	set treediffs($ids) $treediff
-    }
+    set treediffs($ids) $treediff
     unset treepending
     if {$cmitmode eq "tree" && [llength $diffids] == 1} {
 	gettree $diffids