/usr/share/doc/gerris/changelog.Debian.gz is in gerris 20110329-dfsg.2-1build2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gerris/../libgfs-dev/changelog.Debian.gz
/usr/share/doc/gerris/../libgfs-dev/changelog.Debian.gz