When invoking the XML api with a depth of 1 on an GIT based project I get the following stacktrace:

javax.servlet.ServletException: org.kohsuke.stapler.export.NotExportableException: class hudson.plugins.git.opt.PreBuildMergeOptions doesn't have @ExportedBean
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:603)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
org.kohsuke.stapler.MetaClass$4.doDispatch(MetaClass.java:195)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:561)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:233)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:561)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:477)
org.kohsuke.stapler.Stapler.service(Stapler.java:159)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
hudson.plugins.greenballs.GreenBallFilter.doFilter(GreenBallFilter.java:52)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:97)
hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)