Include "a=commit" in direct gitweb commit links

By including the commit action in the gitweb link for a commit the
gitweb CGI has a better idea of what we want it to show for this
object.  If the object isn't present yet (e.g. due to a mirroring
lag) we get a little better error message shown to the client.

Signed-off-by: Shawn O. Pearce <sop@google.com>

src/main/java/com/google/gerrit/client/data/GitwebLink.java

@@ -33,6 +33,7 @@ public class GitwebLink {
   public String toRevision(final Project.NameKey project, final PatchSet ps) {
     final StringBuilder r = new StringBuilder();
     p(r, project);
+    a(r, "commit");
     h(r, ps);
     return baseUrl + r;
   }