gitweb: generate parent..current URLs

gitweb: generate parent..current URLs

If use_pathinfo is enabled, href now creates links that contain paths in
the form $project/$action/oldhash:/oldname..newhash:/newname for actions
that use hash_parent etc.

If any of the filename contains two consecutive dots, it's kept as a CGI
parameter since the resulting path would otherwise be ambiguous.

Signed-off-by: Giuseppe Bilotta <redacted>
Acked-by: Jakub Narebski <redacted>
Signed-off-by: Junio C Hamano <redacted>