Change replacing hashes as from-file/to-file with filenames from
difftree to adding invisible (except underlining on hover/mouseover)
hyperlink to from-file/to-file blob. /dev/null as from-file or
to-file is not changed (is not hyperlinked).
This makes two-file from-file/to-file unified diff header parsing in
git_patchset_body more generic, and not only for legacy blobdiffs.
Signed-off-by: Jakub Narebski <jnareb@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>