git-svn: use ~/.subversion config files when using SVN:: libraries

This allows users to use HTTP proxy information (among other settings)
from ~/.subversion/servers and ~/.subversion/config

--config-dir (as before) may be passed to git-svn to override the
default choice of '~/.subversion' for the configuration directory.

Thanks to tko on #git for pointing this out.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-svn.perl

@@ -2822,7 +2822,9 @@ sub libsvn_connect {
 	    SVN::Client::get_username_prompt_provider(
 	      \&_username_prompt, 2),
 	  ]);
+	my $config = SVN::Core::config_get_config($_config_dir);
 	my $ra = SVN::Ra->new(url => $url, auth => $baton,
+	                      config => $config,
 	                      pool => SVN::Pool->new,
 	                      auth_provider_callbacks => $callbacks);
 	$ra->{svn_path} = $url;
@@ -2834,8 +2836,8 @@ sub libsvn_connect {
 
 sub libsvn_dup_ra {
 	my ($ra) = @_;
-	SVN::Ra->new(map { $_ => $ra->{$_} }
-	             qw/url auth auth_provider_callbacks repos_root svn_path/);
+	SVN::Ra->new(map { $_ => $ra->{$_} } qw/config url
+	             auth auth_provider_callbacks repos_root svn_path/);
 }
 
 sub libsvn_get_file {