[PATCH] gitk: Fix for tree view ending in nested directories

[PATCH] 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.

Signed-off-by: Brian Downing <bdowning@lavos.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>