#include <sys/sockio.h>
#include <sys/sysctl.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <net/bpf.h>
#include <net/if.h>
#include <net/if_types.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_mroute.h>
#include <termios.h>
'

includes_DragonFly='
#include <sys/types.h>
#include <sys/event.h>
#include <sys/socket.h>
#include <sys/sockio.h>

#include <sys/event.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <net/bpf.h>
#include <net/if.h>
#include <net/if_clone.h>
#include <net/if_types.h>
#include <net/route.h>
#include <netinet/in.h>
#include <termios.h>
#include <netinet/ip.h>

* If you declare an exclude, then it includes everything _but_ what is excluded.
* If you declare both includes and excludes, then it includes only what is explicitly included and not excluded.

It is possible to filter either by explicit _group_, _module_ or _version_, either strictly or using regular expressions.

        }

        fileTree.include('*/*included*')
        fileTree.exclude('**/not*')

        expect:
        fileTree.files == [included1, included2] as Set
        assertSetContainsForAllTypes(fileTree, 'subDir/included1', 'subDir2/included2')
        assertVisits(fileTree, ['subDir/included1', 'subDir2/included2'], ['subDir', 'subDir2'])
        fileTree.contains(included1)
        !fileTree.contains(excluded1)

    def included
    def macros = []
    def macroFunctions = []
    def includePaths = [ systemIncludeDir ]

    def setup() {
        included = Mock(IncludeDirectives)
        included.getAllMacros() >> macros
        included.getMacros(_) >> { String name -> macros.findAll {it.name == name} }
        included.hasMacros() >> { !macros.empty }
        included.getAllMacroFunctions() >> macroFunctions

        strictlyEquals(new PatternSet(includes: ['i']), new PatternSet(includes: ['i']))
        strictlyEquals(new PatternSet(excludes: ['e']), new PatternSet(excludes: ['e']))
        strictlyEquals(new PatternSet(includes: ['i'], excludes: ['e']), new PatternSet(includes: ['i'], excludes: ['e']))

        new PatternSet() != new PatternSet(caseSensitive: false)
        new PatternSet() != new PatternSet(includes: ['i'])

    }

    def "discards duplicate includes"() {
        when:
        sourceFile << """
    #include "test1"
    #include "test1"
    #include "test2"
    #include <test1>
    #include <test1>
    #include <test2>
    #include DEFINED
    #include DEFINED
    #include DEFINED()
    #include DEFINED()
    #include DEFINED(ABC)
    #include DEFINED(ABC)
    #include DEFINED(X)
    #include DEFINED(X, Y)

     * @see org.gradle.api.tasks.util.PatternFilterable Pattern Format
     */
    @Override
    CopySpec include(String... includes);

    /**
     * {@inheritDoc}
     *
     * @see org.gradle.api.tasks.util.PatternFilterable Pattern Format
     */
    @Override
    CopySpec include(Iterable<String> includes);

    /**
     * {@inheritDoc}
     *

ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/llvm-3.6/bin/../lib/clang/3.6.0/include
 /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
"""

Using this mechanism, the included build may also contribute a settings plugin that can be applied in the settings file itself:

====
include::sample[dir="snippets/developingPlugins/testingPlugins/kotlin/include-plugin-build",files="settings.gradle.kts[tags=include-build]"]