git-svn: add public property `svn:global-ignores`

Subversion 1.8 added a new property `svn:global-ignores`. It
contains a list of patterns used to determine what files should
be ignored. If Git-SVN is going to ignore these files as well, it
is important that we do not skip over directories that have this
property set.

Signed-off-by: Alex Galvin <agalvin@comqi.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

perl/Git/SVN.pm

@@ -763,7 +763,7 @@ sub prop_walk {
 		# this needs to be updated.
 		++$interesting_props if /^svn:(?:ignore|keywords|executable
 		                                 |eol-style|mime-type
-						 |externals|needs-lock)$/x;
+						 |externals|needs-lock|global-ignores)$/x;
 	}
 	&$sub($self, $p, $props) if $interesting_props;