I created an update-site for set of plugins with a feature.
All is built by tycho and the site is on http server and everything works as it should.
I tried to use the org.eclipse.tycho.extras:tycho-p2-extras-plugin:0.14.0:mirror goal but I get the following error.
<build>
		<plugins>
			<plugin>
				<groupId>org.eclipse.tycho</groupId>
				<artifactId>tycho-p2-director-plugin</artifactId>
				<version>${tycho-version}</version>
				<executions>
					<execution>
						<id>materialize-products</id>
						<goals>
							<goal>materialize-products</goal>
						</goals>
					</execution>
					<execution>
						<id>archive-products</id>
						<goals>
							<goal>archive-products</goal>
						</goals>
					</execution>
				</executions>
			</plugin>
			<plugin>
				<groupId>org.eclipse.tycho.extras</groupId>
				<artifactId>tycho-p2-extras-plugin</artifactId>
				<version>0.14.0</version>
				<executions>
					<execution>
						<phase>package</phase>
						<goals>
							<goal>mirror</goal>
						</goals>
					</execution>
				</executions>
				<configuration>
					<source>
						<!-- source repositories to mirror from -->
						<repository>
                                                          <!-- I removed it from confidentiality reasons --> 
							<url>my-update-site-url</url>
							<layout>p2</layout>
							<!-- supported layouts are "p2-metadata", "p2-artifacts", and "p2" 
								(for joint repositories; default) -->
						</repository>
						<!-- starting from here all configuration parameters are optional -->
						<!-- they are only shown here with default values for documentation 
							purpose -->
						<!-- List of IUs to mirror. If omitted, allIUs will be mirrored. -->
						<!-- Omitted IU version element means latest version of the IU -->
						<!-- <ius> <iu> <id>org.eclipse.rcp.feature.group</id> </iu> </ius> -->
						<!-- The destination directory to mirror to. -->
						<destination>${project.build.directory}/repository</destination>
						<!-- Whether only strict dependencies should be followed. -->
						<!-- "strict" means perfect version match -->
						<followStrictOnly>false</followStrictOnly>
						<!-- Whether or not to follow optional requirements. -->
						<includeOptional>true</includeOptional>
						<!-- Whether or not to follow non-greedy requirements. -->
						<includeNonGreedy>true</includeNonGreedy>
						<!-- Filter properties. E.g. filter only one platform -->
						<!-- Whether to filter the resulting set of IUs to only -->
						<!-- include the latest version of each IU -->
						<latestVersionOnly>false</latestVersionOnly>
						<!-- don't mirror artifacts, only metadata -->
						<mirrorMetadataOnly>false</mirrorMetadataOnly>
						<!-- whether to compress the content.xml/artifacts.xml -->
						<compress>true</compress>
						<!-- whether to append to the target repository content -->
						<append>true</append>
					</source>
				</configuration>
			</plugin>
		</plugins>
	</build>