gitweb: URL-decode $my_url/$my_uri when stripping PATH_INFO

When gitweb is used as a DirectoryIndex, it attempts to strip
PATH_INFO on its own, as $cgi->url() fails to do so.

However, it fails to account for the fact that PATH_INFO has
already been URL-decoded by the web server, but the value
returned by $cgi->url() has not been. This causes the stripping
to fail whenever the URL contains encoded characters.

To see this in action, setup gitweb as a DirectoryIndex and
then use it on a repository with a directory containing a
space in the name. Navigate to tree view, examine the gitweb
generated html and you'll see a link such as:

  <a href="/test.git/tree/HEAD:/directory with spaces">directory with spaces</a>

When clicked on, the browser will URL-encode this link, giving
a $cgi->url() of the form:

   /test.git/tree/HEAD:/directory%20with%20spaces

While PATH_INFO is:

   /test.git/tree/HEAD:/directory with spaces

Fix this by calling unescape() on both $my_url and $my_uri before
stripping PATH_INFO from them.

Signed-off-by: Jay Soffian <redacted>
Acked-by: Jakub Narebski <redacted>
Signed-off-by: Junio C Hamano <redacted>