Add support for downloading archives with /+archive/foo.tar.gz

Support all the archive formats supported upstream in JGit, with the
exception of zip.

Change-Id: I8cdec13882117f5b716e54479cff903d8b25a933

gitiles-servlet/pom.xml

diff --git a/gitiles-servlet/pom.xml b/gitiles-servlet/pom.xml
index 26642e0..4a41bb5 100644
--- a/gitiles-servlet/pom.xml
+++ b/gitiles-servlet/pom.xml
@@ -54,6 +54,11 @@
 
     <dependency>
       <groupId>org.eclipse.jgit</groupId>
+      <artifactId>org.eclipse.jgit.archive</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.eclipse.jgit</groupId>
       <artifactId>org.eclipse.jgit.junit</artifactId>
       <scope>test</scope>
       <exclusions>