delegation: allow includes in fragments, fixup doc

I could not think why we disallowed includes in subconfs, since an
include is the same as inserting all those lines inline anyway.

doc/delegation.mkd

@@ -117,8 +117,9 @@ to the bottom of the main file.
 
 ### other notes
 
-The "include" statement cannot be used in fragment files, for security
-reasons.
+If you're in big-config mode (`GL_BIG_CONFIG` set to 1 in the rc file), a
+fragment file cannot define any new groups; all groups have to be defined in
+the main config file or in a file included from it.
 
 ----
 

doc/gitolite.conf.mkd

@@ -80,9 +80,6 @@ config file exists.
 
 Files that have been already processed once are skipped, with a warning.
 
-[Advanced users: the include statement cannot be used inside a delegated
-config file, for security reasons].
-
 <a name="_basic_access_control"></a>
 
 ### basic access control

src/gl-compile-conf

@@ -257,7 +257,6 @@ sub parse_conf_line
     {
         my $include_glob = $1;
         for my $file (glob($include_glob =~ m(^/) ? $include_glob : "conf/$include_glob")) {
-            die "$ABRT $fragment attempting to include configuration\n" if $fragment ne 'master';
             die "$ABRT included file not found: '$file'\n" unless -f $file;
 
             my $file_id = device_inode($file);