Fix Invalid ref name: HEAD

This exception is related to 5 different errors in datadog logs:

when loading Studio

• Exception while dispatching incoming RPC call

  com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract com.nuxeo.studio.client.model.ProjectModel com.nuxeo.studio.client.rpc.StudioService.getProject(java.lang.String) throws com.nuxeo.studio.core.api.exception.ProjectNotFoundException,com.nuxeo.studio.core.api.exception.BranchNotFoundException,java.io.IOException,com.nuxeo.studio.client.model.ValidationErrorBundle,com.nuxeo.studio.core.api.exception.TargetPlatformNotFoundException' threw an unexpected exception: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#1588-cloned-2019-02-28-18-19-22/.git: Invalid ref name: HEAD
  	at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:416)
  	at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:605)
  	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:333)
  	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:303)
  	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:373)
  	at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
  	at com.nuxeo.studio.servlet.StudioServiceImpl.service(StudioServiceImpl.java:150)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  	...
  	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
  	at java.lang.Thread.run(Thread.java:748)
  Caused by: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#1588-cloned-2019-02-28-18-19-22/.git: Invalid ref name: HEAD
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:459)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnBranch(VersioningAbstract.java:468)
  	at com.nuxeo.studio.core.workspace.WorkspaceProvider.switchToBranch(WorkspaceProvider.java:224)
  	at com.nuxeo.studio.core.api.workspace.Workspace.onBranch(Workspace.java:141)
  	at com.nuxeo.studio.core.workspace.DefaultWorkspacePool.get(DefaultWorkspacePool.java:177)
  	at com.nuxeo.studio.core.workspace.WorkspaceServiceImpl.getWorkspace(WorkspaceServiceImpl.java:41)
  	at com.nuxeo.studio.core.UserPrefsServiceImpl.getUserWorkspace(UserPrefsServiceImpl.java:279)
  	at com.nuxeo.studio.servlet.StudioServiceImpl.getProject(StudioServiceImpl.java:235)
  	at sun.reflect.GeneratedMethodAccessor669.invoke(Unknown Source)
  	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  	at java.lang.reflect.Method.invoke(Method.java:498)
  	at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:587)
  	... 88 more
  Caused by: org.eclipse.jgit.api.errors.JGitInternalException: Invalid ref name: HEAD
  	at org.eclipse.jgit.api.ResetCommand.call(ResetCommand.java:170)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:456)
  	... 99 more
  

• Studio RPC request failed.

  com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract com.nuxeo.studio.client.model.ProjectModel com.nuxeo.studio.client.rpc.StudioService.getProject(java.lang.String) throws com.nuxeo.studio.core.api.exception.ProjectNotFoundException,com.nuxeo.studio.core.api.exception.BranchNotFoundException,java.io.IOException,com.nuxeo.studio.client.model.ValidationErrorBundle,com.nuxeo.studio.core.api.exception.TargetPlatformNotFoundException' threw an unexpected exception: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#1588-cloned-2019-02-28-18-19-22/.git: Invalid ref name: HEAD
  	at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:416)
  	at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:605)
  	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:333)
  	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:303)
  	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:373)
  	at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
  	at com.nuxeo.studio.servlet.StudioServiceImpl.service(StudioServiceImpl.java:150)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	...
  	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
  	at java.lang.Thread.run(Thread.java:748)
  Caused by: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#1588-cloned-2019-02-28-18-19-22/.git: Invalid ref name: HEAD
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:459)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnBranch(VersioningAbstract.java:468)
  	at com.nuxeo.studio.core.workspace.WorkspaceProvider.switchToBranch(WorkspaceProvider.java:224)
  	at com.nuxeo.studio.core.api.workspace.Workspace.onBranch(Workspace.java:141)
  	at com.nuxeo.studio.core.workspace.DefaultWorkspacePool.get(DefaultWorkspacePool.java:177)
  	at com.nuxeo.studio.core.workspace.WorkspaceServiceImpl.getWorkspace(WorkspaceServiceImpl.java:41)
  	at com.nuxeo.studio.core.UserPrefsServiceImpl.getUserWorkspace(UserPrefsServiceImpl.java:279)
  	at com.nuxeo.studio.servlet.StudioServiceImpl.getProject(StudioServiceImpl.java:235)
  	at sun.reflect.GeneratedMethodAccessor669.invoke(Unknown Source)
  	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  	at java.lang.reflect.Method.invoke(Method.java:498)
  	at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:587)
  	... 88 more
  Caused by: org.eclipse.jgit.api.errors.JGitInternalException: Invalid ref name: HEAD
  	at org.eclipse.jgit.api.ResetCommand.call(ResetCommand.java:170)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:456)
  	... 99 more
  

when downloading a package (via hot-reload)

• Error while fetching download

  com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#744-cloned-2019-02-21-15-01-51/.git: Invalid ref name: HEAD
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:459)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnBranch(VersioningAbstract.java:468)
  	at com.nuxeo.studio.core.workspace.WorkspaceProvider.switchToBranch(WorkspaceProvider.java:224)
  	at com.nuxeo.studio.core.api.workspace.Workspace.onBranch(Workspace.java:141)
  	at com.nuxeo.studio.core.workspace.DefaultWorkspacePool.get(DefaultWorkspacePool.java:177)
  	at com.nuxeo.studio.core.workspace.WorkspaceServiceImpl.getWorkspace(WorkspaceServiceImpl.java:41)
  	at com.nuxeo.studio.core.ArtifactServiceImpl.getBranchDefinition(ArtifactServiceImpl.java:397)
  	at com.nuxeo.studio.core.VersionServiceImpl.getAdminCenterVersion(VersionServiceImpl.java:344)
  	at com.nuxeo.connect.packagerepository.PackageRepositoryComponent.getStudioProjectCurrentSnapshot(PackageRepositoryComponent.java:614)
  	at com.nuxeo.connect.gateway.jaxrs.GatewayProvider.lambda$getDownloads$4(GatewayProvider.java:359)
  	at java.util.ArrayList.forEach(ArrayList.java:1249)
  	at com.nuxeo.connect.gateway.jaxrs.GatewayProvider.getDownloads(GatewayProvider.java:358)
  	at com.nuxeo.connect.gateway.jaxrs.GatewayProvider.getDownloads(GatewayProvider.java:252)
  	at sun.reflect.GeneratedMethodAccessor306.invoke(Unknown Source)
  	...
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  	at java.lang.reflect.Method.invoke(Method.java:498)
  	at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
  	at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$TypeOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:185)
  	at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
  	at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:302)
  	at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
  	at com.sun.jersey.server.impl.uri.rules.SubLocatorRule.accept(SubLocatorRule.java:137)
  	at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
  	at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
  	at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
  	at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
  	at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1542)
  	at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1473)
  	at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1419)
  	at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1409)
  	at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:409)
  	at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:558)
  	at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:733)
  	at org.nuxeo.ecm.webengine.app.jersey.WebEngineServlet.containerService(WebEngineServlet.java:178)
  	at org.nuxeo.ecm.webengine.app.jersey.WebEngineServlet.service(WebEngineServlet.java:155)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.elasticsearch.ElasticSearchFilter.doFilter(ElasticSearchFilter.java:55)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.webengine.jaxrs.session.SessionCleanupFilter.run(SessionCleanupFilter.java:50)
  	at org.nuxeo.ecm.webengine.jaxrs.HttpFilter.doFilter(HttpFilter.java:49)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.webengine.app.WebEngineFilter.doFilter(WebEngineFilter.java:92)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.webengine.jaxrs.context.RequestContextFilter.run(RequestContextFilter.java:48)
  	at org.nuxeo.ecm.webengine.jaxrs.HttpFilter.doFilter(HttpFilter.java:49)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at com.nuxeo.connect.filter.SudoFilter.doFilter(SudoFilter.java:60)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at com.nuxeo.connect.filter.ConnectUrlFilter.doFilter(ConnectUrlFilter.java:110)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at com.nuxeo.studio.core.filter.CasPostFilter.run(CasPostFilter.java:45)
  	at org.nuxeo.ecm.webengine.jaxrs.HttpFilter.doFilter(HttpFilter.java:49)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at com.nuxeo.studio.core.session.StudioWebFilter.run(StudioWebFilter.java:64)
  	at org.nuxeo.ecm.webengine.jaxrs.HttpFilter.doFilter(HttpFilter.java:49)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.platform.web.common.requestcontroller.filter.NuxeoThreadTrackerFilter.doFilter(NuxeoThreadTrackerFilter.java:43)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.core.management.jtajca.internal.Log4jWebFilter.doFilter(Log4jWebFilter.java:69)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.platform.ui.web.rest.FancyURLFilter.doFilter(FancyURLFilter.java:120)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.platform.web.common.requestcontroller.filter.NuxeoRequestControllerFilter.doFilter(NuxeoRequestControllerFilter.java:148)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.webdav.service.WIRequestFilter.doFilter(WIRequestFilter.java:61)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilterInternal(NuxeoAuthenticationFilter.java:608)
  	at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:51)
  	at org.nuxeo.ecm.platform.ui.web.auth.oauth.NuxeoOAuthFilter.doFilter(NuxeoOAuthFilter.java:122)
  	at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:49)
  	at org.nuxeo.ecm.platform.ui.web.auth.oauth2.NuxeoOAuth2Filter.doFilter(NuxeoOAuth2Filter.java:82)
  	at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:49)
  	at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilter(NuxeoAuthenticationFilter.java:411)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.platform.web.common.requestcontroller.filter.NuxeoCorsCsrfFilter.doFilter(NuxeoCorsCsrfFilter.java:160)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionFilter.doFilter(NuxeoExceptionFilter.java:77)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.nuxeo.ecm.platform.web.common.encoding.NuxeoEncodingFilter.doFilter(NuxeoEncodingFilter.java:75)
  	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
  	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
  	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
  	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
  	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
  	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
  	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
  	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
  	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
  	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
  	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
  	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
  	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
  	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
  	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
  	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
  	at java.lang.Thread.run(Thread.java:748)
  Caused by: org.eclipse.jgit.api.errors.JGitInternalException: Invalid ref name: HEAD
  	at org.eclipse.jgit.api.ResetCommand.call(ResetCommand.java:170)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:456)
  	... 116 more
  

• Unexpected error

  java.lang.IllegalStateException: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#1588-cloned-2019-02-28-18-19-22/.git: Invalid ref name: HEAD
  	at com.nuxeo.connect.packagerepository.PackageRepositoryComponent.getStudioPackage(PackageRepositoryComponent.java:595)
  	at com.nuxeo.connect.gateway.jaxrs.GatewayProvider.doDownload(GatewayProvider.java:202)
  	at com.nuxeo.connect.gateway.jaxrs.GatewayProvider.getDownload(GatewayProvider.java:138)
  	at sun.reflect.GeneratedMethodAccessor306.invoke(Unknown Source)
  	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  	at java.lang.reflect.Method.invoke(Method.java:498)
  	at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
  	at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$TypeOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:185)
  	at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
  	...
  	at java.lang.Thread.run(Thread.java:748)
  Caused by: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#1588-cloned-2019-02-28-18-19-22/.git: Invalid ref name: HEAD
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:459)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnBranch(VersioningAbstract.java:468)
  	at com.nuxeo.studio.core.workspace.WorkspaceProvider.switchToBranch(WorkspaceProvider.java:224)
  	at com.nuxeo.studio.core.api.workspace.Workspace.onBranch(Workspace.java:141)
  	at com.nuxeo.studio.core.workspace.DefaultWorkspacePool.get(DefaultWorkspacePool.java:177)
  	at com.nuxeo.studio.core.workspace.WorkspaceServiceImpl.getWorkspace(WorkspaceServiceImpl.java:41)
  	at com.nuxeo.studio.core.ArtifactServiceImpl.getBranchDefinition(ArtifactServiceImpl.java:397)
  	at com.nuxeo.studio.core.VersionServiceImpl.getAdminCenterVersion(VersionServiceImpl.java:344)
  	at com.nuxeo.connect.packagerepository.PackageRepositoryComponent.getStudioProjectCurrentSnapshot(PackageRepositoryComponent.java:614)
  	at com.nuxeo.connect.packagerepository.PackageRepositoryComponent.getStudioPackage(PackageRepositoryComponent.java:588)
  	... 106 more
  Caused by: org.eclipse.jgit.api.errors.JGitInternalException: Invalid ref name: HEAD
  	at org.eclipse.jgit.api.ResetCommand.call(ResetCommand.java:170)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:456)
  	... 115 more
  

• Unexpected error during download

  java.lang.IllegalStateException: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#744-cloned-2019-02-21-15-01-51/.git: Invalid ref name: HEAD
  	at com.nuxeo.connect.packagerepository.PackageRepositoryComponent.getStudioPackageFile(PackageRepositoryComponent.java:571)
  	at com.nuxeo.connect.gateway.download.StudioDownloadServlet.doGet(StudioDownloadServlet.java:61)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
  	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
  ...
  	at java.lang.Thread.run(Thread.java:748)
  Caused by: com.nuxeo.studio.core.api.exception.VersioningException: /ebs/studio_workspaces/la-presse/la-presse-#744-cloned-2019-02-21-15-01-51/.git: Invalid ref name: HEAD
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:459)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnBranch(VersioningAbstract.java:468)
  	at com.nuxeo.studio.core.workspace.WorkspaceProvider.switchToBranch(WorkspaceProvider.java:224)
  	at com.nuxeo.studio.core.api.workspace.Workspace.onBranch(Workspace.java:141)
  	at com.nuxeo.studio.core.workspace.DefaultWorkspacePool.get(DefaultWorkspacePool.java:177)
  	at com.nuxeo.studio.core.workspace.WorkspaceServiceImpl.getWorkspace(WorkspaceServiceImpl.java:41)
  	at com.nuxeo.studio.core.ArtifactServiceImpl.getBranchDefinition(ArtifactServiceImpl.java:397)
  	at com.nuxeo.studio.core.VersionServiceImpl.getAdminCenterVersion(VersionServiceImpl.java:344)
  	at com.nuxeo.studio.core.build.StudioPackageBuilder.buildAdminCenter(StudioPackageBuilder.java:52)
  	at com.nuxeo.connect.packagerepository.PackageRepositoryComponent.getStudioPackageFile(PackageRepositoryComponent.java:566)
  	... 70 more
  Caused by: org.eclipse.jgit.api.errors.JGitInternalException: Invalid ref name: HEAD
  	at org.eclipse.jgit.api.ResetCommand.call(ResetCommand.java:170)
  	at com.nuxeo.studio.core.versioning.VersioningAbstract.resetOnHead(VersioningAbstract.java:456)
  	... 79 more