gitk: Fix for tree view ending in nested directories

Unroll the prefix stack when assigning treeheights when leaving proc treeview. Previously, when the ls-tree output ended in multiple nested directories (for instance in a repository with a single file "foo/bar/baz"), $treeheight("foo/bar/") was assigned twice, and $treeheight("foo/") was never assigned. This led to an error when expanding the "foo" directory in the gitk treeview.

---
 gitk |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

index 2d6a6ef..d94c512 100755
@@ -1216,6 +1216,9 @@ proc treeview {w l openlevs} {
 	set treeheight($prefix) $ht
 	incr ht [lindex $htstack end]
 	set htstack [lreplace $htstack end end]
+	set prefixend [lindex $prefendstack end]
+	set prefendstack [lreplace $prefendstack end end]
+	set prefix [string range $prefix 0 $prefixend]
     }
     $w conf -state disabled
 }

1.5.2.GIT