/*
    * Copyright (C) 2008-2010, Google Inc.
    * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
    * Copyright (C) 2013, Matthias Sohn <matthias.sohn@sap.com>
    * Copyright (C) 2017, Thomas Wolf <thomas.wolf@paranor.ch>
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
   * accompanies this distribution, is reproduced below, and is
   * available at http://www.eclipse.org/org/documents/edl-v10.php
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or
   * without modification, are permitted provided that the following
   * conditions are met:
   *
   * - Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   *
   * - Redistributions in binary form must reproduce the above
   *   copyright notice, this list of conditions and the following
   *   disclaimer in the documentation and/or other materials provided
   *   with the distribution.
   *
   * - Neither the name of the Eclipse Foundation, Inc. nor the
   *   names of its contributors may be used to endorse or promote
   *   products derived from this software without specific prior
   *   written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
   * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package org.eclipse.jgit.transport;
  
  import static org.eclipse.jgit.lib.Constants.HEAD;
  import static org.eclipse.jgit.util.HttpSupport.ENCODING_GZIP;
  import static org.eclipse.jgit.util.HttpSupport.ENCODING_X_GZIP;
  import static org.eclipse.jgit.util.HttpSupport.HDR_ACCEPT;
  import static org.eclipse.jgit.util.HttpSupport.HDR_ACCEPT_ENCODING;
  import static org.eclipse.jgit.util.HttpSupport.HDR_CONTENT_ENCODING;
  import static org.eclipse.jgit.util.HttpSupport.HDR_CONTENT_TYPE;
  import static org.eclipse.jgit.util.HttpSupport.HDR_LOCATION;
  import static org.eclipse.jgit.util.HttpSupport.HDR_PRAGMA;
  import static org.eclipse.jgit.util.HttpSupport.HDR_USER_AGENT;
  import static org.eclipse.jgit.util.HttpSupport.HDR_WWW_AUTHENTICATE;
  import static org.eclipse.jgit.util.HttpSupport.METHOD_GET;
  import static org.eclipse.jgit.util.HttpSupport.METHOD_POST;
  
  import java.io.BufferedReader;
  import java.io.ByteArrayInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.net.MalformedURLException;
  import java.net.Proxy;
  import java.net.ProxySelector;
  import java.net.URISyntaxException;
  import java.net.URL;
  import java.security.cert.CertPathBuilderException;
  import java.security.cert.CertPathValidatorException;
  import java.security.cert.CertificateException;
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.EnumSet;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.Locale;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.zip.GZIPInputStream;
  import java.util.zip.GZIPOutputStream;
  
  import javax.net.ssl.SSLHandshakeException;
  
  import org.eclipse.jgit.errors.ConfigInvalidException;
  import org.eclipse.jgit.errors.NoRemoteRepositoryException;
  import org.eclipse.jgit.errors.NotSupportedException;
  import org.eclipse.jgit.errors.PackProtocolException;
  import org.eclipse.jgit.errors.TransportException;
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.internal.storage.file.RefDirectory;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectIdRef;
 import org.eclipse.jgit.lib.ProgressMonitor;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.StoredConfig;
 import org.eclipse.jgit.lib.SymbolicRef;
 import org.eclipse.jgit.storage.file.FileBasedConfig;
 import org.eclipse.jgit.transport.HttpAuthMethod.Type;
 import org.eclipse.jgit.transport.HttpConfig.HttpRedirectMode;
 import org.eclipse.jgit.transport.http.HttpConnection;
 import org.eclipse.jgit.util.FS;
 import org.eclipse.jgit.util.HttpSupport;
 import org.eclipse.jgit.util.IO;
 import org.eclipse.jgit.util.RawParseUtils;
 import org.eclipse.jgit.util.SystemReader;
 import org.eclipse.jgit.util.TemporaryBuffer;
 import org.eclipse.jgit.util.io.DisabledOutputStream;
 import org.eclipse.jgit.util.io.UnionInputStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
  * Transport over HTTP and FTP protocols.
  * <p>
  * If the transport is using HTTP and the remote HTTP service is Git-aware
  * (speaks the "smart-http protocol") this client will automatically take
  * advantage of the additional Git-specific HTTP extensions. If the remote
  * service does not support these extensions, the client will degrade to direct
  * file fetching.
  * <p>
  * If the remote (server side) repository does not have the specialized Git
  * support, object files are retrieved directly through standard HTTP GET (or
  * binary FTP GET) requests. This make it easy to serve a Git repository through
  * a standard web host provider that does not offer specific support for Git.
  *
  * @see WalkFetchConnection
  */
 public class TransportHttp extends HttpTransport implements WalkTransport,
 		PackTransport {
 
 	private static final Logger LOG = LoggerFactory
 			.getLogger(TransportHttp.class);
 
 	private static final String SVC_UPLOAD_PACK = "git-upload-pack"; //$NON-NLS-1$
 
 	private static final String SVC_RECEIVE_PACK = "git-receive-pack"; //$NON-NLS-1$
 
 	/**
 	 * Accept-Encoding header in the HTTP request
 	 * (https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html).
 	 *
 	 * @since 4.6
 	 */
 	public enum AcceptEncoding {
 		/**
 		 * Do not specify an Accept-Encoding header. In most servers this
 		 * results in the content being transmitted as-is.
 		 */
 		UNSPECIFIED,
 
 		/**
 		 * Accept gzip content encoding.
 		 */
 		GZIP
 	}
 
 	static final TransportProtocol PROTO_HTTP = new TransportProtocol() {
 		private final String[] schemeNames = { "http", "https" }; //$NON-NLS-1$ //$NON-NLS-2$
 
 		private final Set<String> schemeSet = Collections
 				.unmodifiableSet(new LinkedHashSet<>(Arrays
 						.asList(schemeNames)));
 
 		@Override
 		public String getName() {
 			return JGitText.get().transportProtoHTTP;
 		}
 
 		@Override
 		public Set<String> getSchemes() {
 			return schemeSet;
 		}
 
 		@Override
 		public Set<URIishField> getRequiredFields() {
 			return Collections.unmodifiableSet(EnumSet.of(URIishField.HOST,
 					URIishField.PATH));
 		}
 
 		@Override
 		public Set<URIishField> getOptionalFields() {
 			return Collections.unmodifiableSet(EnumSet.of(URIishField.USER,
 					URIishField.PASS, URIishField.PORT));
 		}
 
 		@Override
 		public int getDefaultPort() {
 			return 80;
 		}
 
 		@Override
 		public Transport open(URIish uri, Repository local, String remoteName)
 				throws NotSupportedException {
 			return new TransportHttp(local, uri);
 		}
 
 		@Override
 		public Transport open(URIish uri) throws NotSupportedException {
 			return new TransportHttp(uri);
 		}
 	};
 
 	static final TransportProtocol PROTO_FTP = new TransportProtocol() {
 		@Override
 		public String getName() {
 			return JGitText.get().transportProtoFTP;
 		}
 
 		@Override
 		public Set<String> getSchemes() {
 			return Collections.singleton("ftp"); //$NON-NLS-1$
 		}
 
 		@Override
 		public Set<URIishField> getRequiredFields() {
 			return Collections.unmodifiableSet(EnumSet.of(URIishField.HOST,
 					URIishField.PATH));
 		}
 
 		@Override
 		public Set<URIishField> getOptionalFields() {
 			return Collections.unmodifiableSet(EnumSet.of(URIishField.USER,
 					URIishField.PASS, URIishField.PORT));
 		}
 
 		@Override
 		public int getDefaultPort() {
 			return 21;
 		}
 
 		@Override
 		public Transport open(URIish uri, Repository local, String remoteName)
 				throws NotSupportedException {
 			return new TransportHttp(local, uri);
 		}
 	};
 
 	/**
 	 * The current URI we're talking to. The inherited (final) field
 	 * {@link #uri} stores the original URI; {@code currentUri} may be different
 	 * after redirects.
 	 */
 	private URIish currentUri;
 
 	private URL baseUrl;
 
 	private URL objectsUrl;
 
 	private final HttpConfig http;
 
 	private final ProxySelector proxySelector;
 
 	private boolean useSmartHttp = true;
 
 	private HttpAuthMethod authMethod = HttpAuthMethod.Type.NONE.method(null);
 
 	private Map<String, String> headers;
 
 	private boolean sslVerify;
 
 	private boolean sslFailure = false;
 
 	TransportHttp(final Repository local, final URIish uri)
 			throws NotSupportedException {
 		super(local, uri);
 		setURI(uri);
 		http = new HttpConfig(local.getConfig(), uri);
 		proxySelector = ProxySelector.getDefault();
 		sslVerify = http.isSslVerify();
 	}
 
 	private URL toURL(URIish urish) throws MalformedURLException {
 		String uriString = urish.toString();
 		if (!uriString.endsWith("/")) { //$NON-NLS-1$
 			uriString += '/';
 		}
 		return new URL(uriString);
 	}
 
 	/**
 	 * @param uri
 	 * @throws NotSupportedException
 	 * @since 4.9
 	 */
 	protected void setURI(final URIish uri) throws NotSupportedException {
 		try {
 			currentUri = uri;
 			baseUrl = toURL(uri);
 			objectsUrl = new URL(baseUrl, "objects/"); //$NON-NLS-1$
 		} catch (MalformedURLException e) {
 			throw new NotSupportedException(MessageFormat.format(JGitText.get().invalidURL, uri), e);
 		}
 	}
 
 	/**
 	 * Create a minimal HTTP transport with default configuration values.
 	 *
 	 * @param uri
 	 * @throws NotSupportedException
 	 */
 	TransportHttp(final URIish uri) throws NotSupportedException {
 		super(uri);
 		setURI(uri);
 		http = new HttpConfig(uri);
 		proxySelector = ProxySelector.getDefault();
 		sslVerify = http.isSslVerify();
 	}
 
 	/**
 	 * Toggle whether or not smart HTTP transport should be used.
 	 * <p>
 	 * This flag exists primarily to support backwards compatibility testing
 	 * within a testing framework, there is no need to modify it in most
 	 * applications.
 	 *
 	 * @param on
 	 *            if {@code true} (default), smart HTTP is enabled.
 	 */
 	public void setUseSmartHttp(final boolean on) {
 		useSmartHttp = on;
 	}
 
 	@Override
 	public FetchConnection openFetch() throws TransportException,
 			NotSupportedException {
 		final String service = SVC_UPLOAD_PACK;
 		try {
 			final HttpConnection c = connect(service);
 			final InputStream in = openInputStream(c);
 			try {
 				BaseConnection f;
 				if (isSmartHttp(c, service)) {
 					readSmartHeaders(in, service);
 					f = new SmartHttpFetchConnection(in);
 				} else {
 					// Assume this server doesn't support smart HTTP fetch
 					// and fall back on dumb object walking.
 					f = newDumbConnection(in);
 				}
 				f.setPeerUserAgent(c.getHeaderField(HttpSupport.HDR_SERVER));
 				return (FetchConnection) f;
 			} finally {
 				in.close();
 			}
 		} catch (NotSupportedException err) {
 			throw err;
 		} catch (TransportException err) {
 			throw err;
 		} catch (IOException err) {
 			throw new TransportException(uri, JGitText.get().errorReadingInfoRefs, err);
 		}
 	}
 
 	private WalkFetchConnection newDumbConnection(InputStream in)
 			throws IOException, PackProtocolException {
 		HttpObjectDB d = new HttpObjectDB(objectsUrl);
 		BufferedReader br = toBufferedReader(in);
 		Map<String, Ref> refs;
 		try {
 			refs = d.readAdvertisedImpl(br);
 		} finally {
 			br.close();
 		}
 
 		if (!refs.containsKey(HEAD)) {
 			// If HEAD was not published in the info/refs file (it usually
 			// is not there) download HEAD by itself as a loose file and do
 			// the resolution by hand.
 			//
 			HttpConnection conn = httpOpen(
 					METHOD_GET,
 					new URL(baseUrl, HEAD),
 					AcceptEncoding.GZIP);
 			int status = HttpSupport.response(conn);
 			switch (status) {
 			case HttpConnection.HTTP_OK: {
 				br = toBufferedReader(openInputStream(conn));
 				try {
 					String line = br.readLine();
 					if (line != null && line.startsWith(RefDirectory.SYMREF)) {
 						String target = line.substring(RefDirectory.SYMREF.length());
 						Ref r = refs.get(target);
 						if (r == null)
 							r = new ObjectIdRef.Unpeeled(Ref.Storage.NEW, target, null);
 						r = new SymbolicRef(HEAD, r);
 						refs.put(r.getName(), r);
 					} else if (line != null && ObjectId.isId(line)) {
 						Ref r = new ObjectIdRef.Unpeeled(Ref.Storage.NETWORK,
 								HEAD, ObjectId.fromString(line));
 						refs.put(r.getName(), r);
 					}
 				} finally {
 					br.close();
 				}
 				break;
 			}
 
 			case HttpConnection.HTTP_NOT_FOUND:
 				break;
 
 			default:
 				throw new TransportException(uri, MessageFormat.format(
 						JGitText.get().cannotReadHEAD, Integer.valueOf(status),
 						conn.getResponseMessage()));
 			}
 		}
 
 		WalkFetchConnection wfc = new WalkFetchConnection(this, d);
 		wfc.available(refs);
 		return wfc;
 	}
 
 	private BufferedReader toBufferedReader(InputStream in) {
 		return new BufferedReader(new InputStreamReader(in, Constants.CHARSET));
 	}
 
 	@Override
 	public PushConnection openPush() throws NotSupportedException,
 			TransportException {
 		final String service = SVC_RECEIVE_PACK;
 		try {
 			final HttpConnection c = connect(service);
 			final InputStream in = openInputStream(c);
 			try {
 				if (isSmartHttp(c, service)) {
 					return smartPush(service, c, in);
 				} else if (!useSmartHttp) {
 					final String msg = JGitText.get().smartHTTPPushDisabled;
 					throw new NotSupportedException(msg);
 
 				} else {
 					final String msg = JGitText.get().remoteDoesNotSupportSmartHTTPPush;
 					throw new NotSupportedException(msg);
 				}
 			} finally {
 				in.close();
 			}
 		} catch (NotSupportedException err) {
 			throw err;
 		} catch (TransportException err) {
 			throw err;
 		} catch (IOException err) {
 			throw new TransportException(uri, JGitText.get().errorReadingInfoRefs, err);
 		}
 	}
 
 	private PushConnection smartPush(String service, HttpConnection c,
 			InputStream in) throws IOException, TransportException {
 		readSmartHeaders(in, service);
 		SmartHttpPushConnection p = new SmartHttpPushConnection(in);
 		p.setPeerUserAgent(c.getHeaderField(HttpSupport.HDR_SERVER));
 		return p;
 	}
 
 	@Override
 	public void close() {
 		// No explicit connections are maintained.
 	}
 
 	/**
 	 * Set additional headers on the HTTP connection
 	 *
 	 * @param headers
 	 *            a map of name:values that are to be set as headers on the HTTP
 	 *            connection
 	 * @since 3.4
 	 */
 	public void setAdditionalHeaders(Map<String, String> headers) {
 		this.headers = headers;
 	}
 
 	private HttpConnection connect(final String service)
 			throws TransportException, NotSupportedException {
 		URL u = getServiceURL(service);
 		int authAttempts = 1;
 		int redirects = 0;
 		Collection<Type> ignoreTypes = null;
 		for (;;) {
 			try {
 				final HttpConnection conn = httpOpen(METHOD_GET, u, AcceptEncoding.GZIP);
 				if (useSmartHttp) {
 					String exp = "application/x-" + service + "-advertisement"; //$NON-NLS-1$ //$NON-NLS-2$
 					conn.setRequestProperty(HDR_ACCEPT, exp + ", */*"); //$NON-NLS-1$
 				} else {
 					conn.setRequestProperty(HDR_ACCEPT, "*/*"); //$NON-NLS-1$
 				}
 				final int status = HttpSupport.response(conn);
 				switch (status) {
 				case HttpConnection.HTTP_OK:
 					// Check if HttpConnection did some authentication in the
 					// background (e.g Kerberos/SPNEGO).
 					// That may not work for streaming requests and jgit
 					// explicit authentication would be required
 					if (authMethod.getType() == HttpAuthMethod.Type.NONE
 							&& conn.getHeaderField(HDR_WWW_AUTHENTICATE) != null)
 						authMethod = HttpAuthMethod.scanResponse(conn, ignoreTypes);
 					return conn;
 
 				case HttpConnection.HTTP_NOT_FOUND:
 					throw new NoRemoteRepositoryException(uri,
 							MessageFormat.format(JGitText.get().uriNotFound, u));
 
 				case HttpConnection.HTTP_UNAUTHORIZED:
 					authMethod = HttpAuthMethod.scanResponse(conn, ignoreTypes);
 					if (authMethod.getType() == HttpAuthMethod.Type.NONE)
 						throw new TransportException(uri, MessageFormat.format(
 								JGitText.get().authenticationNotSupported, uri));
 					CredentialsProvider credentialsProvider = getCredentialsProvider();
 					if (credentialsProvider == null)
 						throw new TransportException(uri,
 								JGitText.get().noCredentialsProvider);
 					if (authAttempts > 1)
 						credentialsProvider.reset(currentUri);
 					if (3 < authAttempts
 							|| !authMethod.authorize(currentUri,
 									credentialsProvider)) {
 						throw new TransportException(uri,
 								JGitText.get().notAuthorized);
 					}
 					authAttempts++;
 					continue;
 
 				case HttpConnection.HTTP_FORBIDDEN:
 					throw new TransportException(uri, MessageFormat.format(
 							JGitText.get().serviceNotPermitted, baseUrl,
 							service));
 
 				case HttpConnection.HTTP_MOVED_PERM:
 				case HttpConnection.HTTP_MOVED_TEMP:
 				case HttpConnection.HTTP_SEE_OTHER:
 				case HttpConnection.HTTP_11_MOVED_TEMP:
 					// SEE_OTHER should actually never be sent by a git server,
 					// and in general should occur only on POST requests. But it
 					// doesn't hurt to accept it here as a redirect.
 					if (http.getFollowRedirects() == HttpRedirectMode.FALSE) {
 						throw new TransportException(uri,
 								MessageFormat.format(
 										JGitText.get().redirectsOff,
 										Integer.valueOf(status)));
 					}
 					URIish newUri = redirect(conn.getHeaderField(HDR_LOCATION),
 							Constants.INFO_REFS, redirects++);
 					setURI(newUri);
 					u = getServiceURL(service);
 					authAttempts = 1;
 					break;
 				default:
 					String err = status + " " + conn.getResponseMessage(); //$NON-NLS-1$
 					throw new TransportException(uri, err);
 				}
 			} catch (NotSupportedException e) {
 				throw e;
 			} catch (TransportException e) {
 				throw e;
 			} catch (SSLHandshakeException e) {
 				handleSslFailure(e);
 				continue; // Re-try
 			} catch (IOException e) {
 				if (authMethod.getType() != HttpAuthMethod.Type.NONE) {
 					if (ignoreTypes == null) {
 						ignoreTypes = new HashSet<>();
 					}
 
 					ignoreTypes.add(authMethod.getType());
 
 					// reset auth method & attempts for next authentication type
 					authMethod = HttpAuthMethod.Type.NONE.method(null);
 					authAttempts = 1;
 
 					continue;
 				}
 
 				throw new TransportException(uri, MessageFormat.format(JGitText.get().cannotOpenService, service), e);
 			}
 		}
 	}
 
 	private static class CredentialItems {
 		CredentialItem.InformationalMessage message;
 
 		/** Trust the server for this git operation */
 		CredentialItem.YesNoType now;
 
 		/**
 		 * Trust the server for all git operations from this repository; may be
 		 * {@code null} if the transport was created via
 		 * {@link #TransportHttp(URIish)}.
 		 */
 		CredentialItem.YesNoType forRepo;
 
 		/** Always trust the server from now on. */
 		CredentialItem.YesNoType always;
 
 		public CredentialItem[] items() {
 			if (forRepo == null) {
 				return new CredentialItem[] { message, now, always };
 			} else {
 				return new CredentialItem[] { message, now, forRepo, always };
 			}
 		}
 	}
 
 	private void handleSslFailure(Throwable e) throws TransportException {
 		if (sslFailure || !trustInsecureSslConnection(e.getCause())) {
 			throw new TransportException(uri,
 					MessageFormat.format(
 							JGitText.get().sslFailureExceptionMessage,
 							currentUri.setPass(null)),
 					e);
 		}
 		sslFailure = true;
 	}
 
 	private boolean trustInsecureSslConnection(Throwable cause) {
 		if (cause instanceof CertificateException
 				|| cause instanceof CertPathBuilderException
 				|| cause instanceof CertPathValidatorException) {
 			// Certificate expired or revoked, PKIX path building not
 			// possible, self-signed certificate, host does not match ...
 			CredentialsProvider provider = getCredentialsProvider();
 			if (provider != null) {
 				CredentialItems trust = constructSslTrustItems(cause);
 				CredentialItem[] items = trust.items();
 				if (provider.supports(items)) {
 					boolean answered = provider.get(uri, items);
 					if (answered) {
 						// Not canceled
 						boolean trustNow = trust.now.getValue();
 						boolean trustLocal = trust.forRepo != null
 								&& trust.forRepo.getValue();
 						boolean trustAlways = trust.always.getValue();
 						if (trustNow || trustLocal || trustAlways) {
 							sslVerify = false;
 							if (trustAlways) {
 								updateSslVerifyUser(false);
 							} else if (trustLocal) {
 								updateSslVerify(local.getConfig(), false);
 							}
 							return true;
 						}
 					}
 				}
 			}
 		}
 		return false;
 	}
 
 	private CredentialItems constructSslTrustItems(Throwable cause) {
 		CredentialItems items = new CredentialItems();
 		String info = MessageFormat.format(JGitText.get().sslFailureInfo,
 				currentUri.setPass(null));
 		String sslMessage = cause.getLocalizedMessage();
 		if (sslMessage == null) {
 			sslMessage = cause.toString();
 		}
 		sslMessage = MessageFormat.format(JGitText.get().sslFailureCause,
 				sslMessage);
 		items.message = new CredentialItem.InformationalMessage(info + '\n'
 				+ sslMessage + '\n'
 				+ JGitText.get().sslFailureTrustExplanation);
 		items.now = new CredentialItem.YesNoType(JGitText.get().sslTrustNow);
 		if (local != null) {
 			items.forRepo = new CredentialItem.YesNoType(
 					MessageFormat.format(JGitText.get().sslTrustForRepo,
 					local.getDirectory()));
 		}
 		items.always = new CredentialItem.YesNoType(
 				JGitText.get().sslTrustAlways);
 		return items;
 	}
 
 	private void updateSslVerify(StoredConfig config, boolean value) {
 		// Since git uses the original URI for matching, we must also use the
 		// original URI and cannot use the current URI (which might be different
 		// after redirects).
 		String uriPattern = uri.getScheme() + "://" + uri.getHost(); //$NON-NLS-1$
 		int port = uri.getPort();
 		if (port > 0) {
 			uriPattern += ":" + port; //$NON-NLS-1$
 		}
 		config.setBoolean(HttpConfig.HTTP, uriPattern,
 				HttpConfig.SSL_VERIFY_KEY, value);
 		try {
 			config.save();
 		} catch (IOException e) {
 			LOG.error(JGitText.get().sslVerifyCannotSave, e);
 		}
 	}
 
 	private void updateSslVerifyUser(boolean value) {
 		FileBasedConfig userConfig = SystemReader.getInstance()
 				.openUserConfig(null, FS.DETECTED);
 		try {
 			userConfig.load();
 			updateSslVerify(userConfig, value);
 		} catch (IOException | ConfigInvalidException e) {
 			// Log it, but otherwise ignore here.
 			LOG.error(MessageFormat.format(JGitText.get().userConfigFileInvalid,
 					userConfig.getFile().getAbsolutePath(), e));
 		}
 	}
 
 	private URIish redirect(String location, String checkFor, int redirects)
 			throws TransportException {
 		if (location == null || location.isEmpty()) {
 			throw new TransportException(uri,
 					MessageFormat.format(JGitText.get().redirectLocationMissing,
 							baseUrl));
 		}
 		if (redirects >= http.getMaxRedirects()) {
 			throw new TransportException(uri,
 					MessageFormat.format(JGitText.get().redirectLimitExceeded,
 							Integer.valueOf(http.getMaxRedirects()), baseUrl,
 							location));
 		}
 		try {
 			if (!isValidRedirect(baseUrl, location, checkFor)) {
 				throw new TransportException(uri,
 						MessageFormat.format(JGitText.get().redirectBlocked,
 								baseUrl, location));
 			}
 			location = location.substring(0, location.indexOf(checkFor));
 			URIish result = new URIish(location);
 			if (LOG.isInfoEnabled()) {
 				LOG.info(MessageFormat.format(JGitText.get().redirectHttp,
 						uri.setPass(null),
 						Integer.valueOf(redirects), baseUrl, result));
 			}
 			return result;
 		} catch (URISyntaxException e) {
 			throw new TransportException(uri,
 					MessageFormat.format(JGitText.get().invalidRedirectLocation,
 							baseUrl, location),
 					e);
 		}
 	}
 
 	private boolean isValidRedirect(URL current, String next, String checkFor) {
 		// Protocols must be the same, or current is "http" and next "https". We
 		// do not follow redirects from https back to http.
 		String oldProtocol = current.getProtocol().toLowerCase(Locale.ROOT);
 		int schemeEnd = next.indexOf("://"); //$NON-NLS-1$
 		if (schemeEnd < 0) {
 			return false;
 		}
 		String newProtocol = next.substring(0, schemeEnd)
 				.toLowerCase(Locale.ROOT);
 		if (!oldProtocol.equals(newProtocol)) {
 			if (!"https".equals(newProtocol)) { //$NON-NLS-1$
 				return false;
 			}
 		}
 		// git allows only rewriting the root, i.e., everything before INFO_REFS
 		// or the service name
 		if (next.indexOf(checkFor) < 0) {
 			return false;
 		}
 		// Basically we should test here that whatever follows INFO_REFS is
 		// unchanged. But since we re-construct the query part
 		// anyway, it doesn't matter.
 		return true;
 	}
 
 	private URL getServiceURL(final String service)
 			throws NotSupportedException {
 		try {
 			final StringBuilder b = new StringBuilder();
 			b.append(baseUrl);
 
 			if (b.charAt(b.length() - 1) != '/') {
 				b.append('/');
 			}
 			b.append(Constants.INFO_REFS);
 
 			if (useSmartHttp) {
 				b.append(b.indexOf("?") < 0 ? '?' : '&'); //$NON-NLS-1$
 				b.append("service="); //$NON-NLS-1$
 				b.append(service);
 			}
 
 			return new URL(b.toString());
 		} catch (MalformedURLException e) {
 			throw new NotSupportedException(MessageFormat.format(JGitText.get().invalidURL, uri), e);
 		}
 	}
 
 	/**
 	 * Open an HTTP connection, setting the accept-encoding request header to gzip.
 	 *
 	 * @param method HTTP request method
 	 * @param u url of the HTTP connection
 	 * @return the HTTP connection
 	 * @throws IOException
 	 * @since 3.3
 	 * @deprecated use {@link #httpOpen(String, URL, AcceptEncoding)} instead.
 	 */
 	@Deprecated
 	protected HttpConnection httpOpen(String method, URL u) throws IOException {
 		return httpOpen(method, u, AcceptEncoding.GZIP);
 	}
 
 	/**
 	 * Open an HTTP connection.
 	 *
 	 * @param method HTTP request method
 	 * @param u url of the HTTP connection
 	 * @param acceptEncoding accept-encoding header option
 	 * @return the HTTP connection
 	 * @throws IOException
 	 * @since 4.6
 	 */
 	protected HttpConnection httpOpen(String method, URL u,
 			AcceptEncoding acceptEncoding) throws IOException {
 		if (method == null || u == null || acceptEncoding == null) {
 			throw new NullPointerException();
 		}
 
 		final Proxy proxy = HttpSupport.proxyFor(proxySelector, u);
 		HttpConnection conn = connectionFactory.create(u, proxy);
 
 		if (!sslVerify && "https".equals(u.getProtocol())) { //$NON-NLS-1$
 			HttpSupport.disableSslVerify(conn);
 		}
 
 		// We must do our own redirect handling to implement git rules and to
 		// handle http->https redirects
 		conn.setInstanceFollowRedirects(false);
 
 		conn.setRequestMethod(method);
 		conn.setUseCaches(false);
 		if (acceptEncoding == AcceptEncoding.GZIP) {
 			conn.setRequestProperty(HDR_ACCEPT_ENCODING, ENCODING_GZIP);
 		}
 		conn.setRequestProperty(HDR_PRAGMA, "no-cache"); //$NON-NLS-1$
 		if (UserAgent.get() != null) {
 			conn.setRequestProperty(HDR_USER_AGENT, UserAgent.get());
 		}
 		int timeOut = getTimeout();
 		if (timeOut != -1) {
 			int effTimeOut = timeOut * 1000;
 			conn.setConnectTimeout(effTimeOut);
 			conn.setReadTimeout(effTimeOut);
 		}
 		if (this.headers != null && !this.headers.isEmpty()) {
 			for (Map.Entry<String, String> entry : this.headers.entrySet())
 				conn.setRequestProperty(entry.getKey(), entry.getValue());
 		}
 		authMethod.configureRequest(conn);
 		return conn;
 	}
 
 	final InputStream openInputStream(HttpConnection conn)
 			throws IOException {
 		InputStream input = conn.getInputStream();
 		if (isGzipContent(conn))
 			input = new GZIPInputStream(input);
 		return input;
 	}
 
 	IOException wrongContentType(String expType, String actType) {
 		final String why = MessageFormat.format(JGitText.get().expectedReceivedContentType, expType, actType);
 		return new TransportException(uri, why);
 	}
 
 	private boolean isSmartHttp(final HttpConnection c, final String service) {
 		final String expType = "application/x-" + service + "-advertisement"; //$NON-NLS-1$ //$NON-NLS-2$
 		final String actType = c.getContentType();
 		return expType.equals(actType);
 	}
 
 	private boolean isGzipContent(final HttpConnection c) {
 		return ENCODING_GZIP.equals(c.getHeaderField(HDR_CONTENT_ENCODING))
 				|| ENCODING_X_GZIP.equals(c.getHeaderField(HDR_CONTENT_ENCODING));
 	}
 
 	private void readSmartHeaders(final InputStream in, final String service)
 			throws IOException {
 		// A smart reply will have a '#' after the first 4 bytes, but
 		// a dumb reply cannot contain a '#' until after byte 41. Do a
 		// quick check to make sure its a smart reply before we parse
 		// as a pkt-line stream.
 		//
 		final byte[] magic = new byte[5];
 		IO.readFully(in, magic, 0, magic.length);
 		if (magic[4] != '#') {
 			throw new TransportException(uri, MessageFormat.format(
 					JGitText.get().expectedPktLineWithService, RawParseUtils.decode(magic)));
 		}
 
 		final PacketLineIn pckIn = new PacketLineIn(new UnionInputStream(
 				new ByteArrayInputStream(magic), in));
 		final String exp = "# service=" + service; //$NON-NLS-1$
 		final String act = pckIn.readString();
 		if (!exp.equals(act)) {
 			throw new TransportException(uri, MessageFormat.format(
 					JGitText.get().expectedGot, exp, act));
 		}
 
 		while (pckIn.readString() != PacketLineIn.END) {
 			// for now, ignore the remaining header lines
 		}
 	}
 
 	class HttpObjectDB extends WalkRemoteObjectDatabase {
 		private final URL httpObjectsUrl;
 
 		HttpObjectDB(final URL b) {
 			httpObjectsUrl = b;
 		}
 
 		@Override
 		URIish getURI() {
 			return new URIish(httpObjectsUrl);
 		}
 
 		@Override
 		Collection<WalkRemoteObjectDatabase> getAlternates() throws IOException {
 			try {
 				return readAlternates(INFO_HTTP_ALTERNATES);
 			} catch (FileNotFoundException err) {
 				// Fall through.
 			}
 
 			try {
 				return readAlternates(INFO_ALTERNATES);
 			} catch (FileNotFoundException err) {
 				// Fall through.
 			}
 
 			return null;
 		}
 
 		@Override
 		WalkRemoteObjectDatabase openAlternate(final String location)
 				throws IOException {
 			return new HttpObjectDB(new URL(httpObjectsUrl, location));
 		}
 
 		@Override
 		BufferedReader openReader(String path) throws IOException {
 			// Line oriented readable content is likely to compress well.
 			// Request gzip encoding.
 			InputStream is = open(path, AcceptEncoding.GZIP).in;
 			return new BufferedReader(new InputStreamReader(is, Constants.CHARSET));
 		}
 
 		@Override
 		Collection<String> getPackNames() throws IOException {
 			final Collection<String> packs = new ArrayList<>();
 			try {
 				final BufferedReader br = openReader(INFO_PACKS);
 				try {
 					for (;;) {
 						final String s = br.readLine();
 						if (s == null || s.length() == 0)
 							break;
 						if (!s.startsWith("P pack-") || !s.endsWith(".pack")) //$NON-NLS-1$ //$NON-NLS-2$
 							throw invalidAdvertisement(s);
 						packs.add(s.substring(2));
 					}
 					return packs;
 				} finally {
 					br.close();
 				}
 			} catch (FileNotFoundException err) {
 				return packs;
 			}
 		}
 
 		@Override
 		FileStream open(final String path) throws IOException {
 			return open(path, AcceptEncoding.UNSPECIFIED);
 		}
 
 		FileStream open(String path, AcceptEncoding acceptEncoding)
 				throws IOException {
 			final URL base = httpObjectsUrl;
 			final URL u = new URL(base, path);
 			final HttpConnection c = httpOpen(METHOD_GET, u, acceptEncoding);
 			switch (HttpSupport.response(c)) {
 			case HttpConnection.HTTP_OK:
 				final InputStream in = openInputStream(c);
 				// If content is being gzipped and then transferred, the content
 				// length in the header is the zipped content length, not the
 				// actual content length.
 				if (!isGzipContent(c)) {
 					final int len = c.getContentLength();
 					return new FileStream(in, len);
 				}
 				return new FileStream(in);
 			case HttpConnection.HTTP_NOT_FOUND:
 				throw new FileNotFoundException(u.toString());
 			default:
 				throw new IOException(u.toString() + ": " //$NON-NLS-1$
 						+ HttpSupport.response(c) + " " //$NON-NLS-1$
 						+ c.getResponseMessage());
 			}
 		}
 
 		Map<String, Ref> readAdvertisedImpl(final BufferedReader br)
 				throws IOException, PackProtocolException {
 			final TreeMap<String, Ref> avail = new TreeMap<>();
 			for (;;) {
 				String line = br.readLine();
 				if (line == null)
 					break;
 
 				final int tab = line.indexOf('\t');
 				if (tab < 0)
 					throw invalidAdvertisement(line);
 
 				String name;
 				final ObjectId id;
 
 				name = line.substring(tab + 1);
 				id = ObjectId.fromString(line.substring(0, tab));
 				if (name.endsWith("^{}")) { //$NON-NLS-1$
 					name = name.substring(0, name.length() - 3);
 					final Ref prior = avail.get(name);
 					if (prior == null)
 						throw outOfOrderAdvertisement(name);
 
 					if (prior.getPeeledObjectId() != null)
 						throw duplicateAdvertisement(name + "^{}"); //$NON-NLS-1$
 
 					avail.put(name, new ObjectIdRef.PeeledTag(
 							Ref.Storage.NETWORK, name,
 							prior.getObjectId(), id));
 				} else {
 					Ref prior = avail.put(name, new ObjectIdRef.PeeledNonTag(
 							Ref.Storage.NETWORK, name, id));
 					if (prior != null)
 						throw duplicateAdvertisement(name);
 				}
 			}
 			return avail;
 		}
 
 		private PackProtocolException outOfOrderAdvertisement(final String n) {
 			return new PackProtocolException(MessageFormat.format(JGitText.get().advertisementOfCameBefore, n, n));
 		}
 
 		private PackProtocolException invalidAdvertisement(final String n) {
 			return new PackProtocolException(MessageFormat.format(JGitText.get().invalidAdvertisementOf, n));
 		}
 
 		private PackProtocolException duplicateAdvertisement(final String n) {
 			return new PackProtocolException(MessageFormat.format(JGitText.get().duplicateAdvertisementsOf, n));
 		}
 
 		@Override
 		void close() {
 			// We do not maintain persistent connections.
 		}
 	}
 
 	class SmartHttpFetchConnection extends BasePackFetchConnection {
 		private MultiRequestService svc;
 
 		SmartHttpFetchConnection(final InputStream advertisement)
 				throws TransportException {
 			super(TransportHttp.this);
 			statelessRPC = true;
 
 			init(advertisement, DisabledOutputStream.INSTANCE);
 			outNeedsEnd = false;
 			readAdvertisedRefs();
 		}
 
 		@Override
 		protected void doFetch(final ProgressMonitor monitor,
 				final Collection<Ref> want, final Set<ObjectId> have,
 				final OutputStream outputStream) throws TransportException {
 			try {
 				svc = new MultiRequestService(SVC_UPLOAD_PACK);
 				init(svc.getInputStream(), svc.getOutputStream());
 				super.doFetch(monitor, want, have, outputStream);
 			} finally {
 				svc = null;
 			}
 		}
 
 		@Override
 		protected void onReceivePack() {
 			svc.finalRequest = true;
 		}
 	}
 
 	class SmartHttpPushConnection extends BasePackPushConnection {
 		SmartHttpPushConnection(final InputStream advertisement)
 				throws TransportException {
 			super(TransportHttp.this);
 			statelessRPC = true;
 
 			init(advertisement, DisabledOutputStream.INSTANCE);
 			outNeedsEnd = false;
 			readAdvertisedRefs();
 		}
 
 		@Override
 		protected void doPush(final ProgressMonitor monitor,
 				final Map<String, RemoteRefUpdate> refUpdates,
 				OutputStream outputStream) throws TransportException {
 			final Service svc = new MultiRequestService(SVC_RECEIVE_PACK);
 			init(svc.getInputStream(), svc.getOutputStream());
 			super.doPush(monitor, refUpdates, outputStream);
 		}
 	}
 
 	/** Basic service for sending and receiving HTTP requests. */
 	abstract class Service {
 		protected final String serviceName;
 
 		protected final String requestType;
 
 		protected final String responseType;
 
 		protected HttpConnection conn;
 
 		protected HttpOutputStream out;
 
 		protected final HttpExecuteStream execute;
 
 		final UnionInputStream in;
 
 		Service(String serviceName) {
 			this.serviceName = serviceName;
 			this.requestType = "application/x-" + serviceName + "-request"; //$NON-NLS-1$ //$NON-NLS-2$
 			this.responseType = "application/x-" + serviceName + "-result"; //$NON-NLS-1$ //$NON-NLS-2$
 
 			this.out = new HttpOutputStream();
 			this.execute = new HttpExecuteStream();
 			this.in = new UnionInputStream(execute);
 		}
 
 		void openStream() throws IOException {
 			conn = httpOpen(METHOD_POST, new URL(baseUrl, serviceName),
 					AcceptEncoding.GZIP);
 			conn.setInstanceFollowRedirects(false);
 			conn.setDoOutput(true);
 			conn.setRequestProperty(HDR_CONTENT_TYPE, requestType);
 			conn.setRequestProperty(HDR_ACCEPT, responseType);
 		}
 
 		void sendRequest() throws IOException {
 			// Try to compress the content, but only if that is smaller.
 			TemporaryBuffer buf = new TemporaryBuffer.Heap(
 					http.getPostBuffer());
 			try {
 				GZIPOutputStream gzip = new GZIPOutputStream(buf);
 				out.writeTo(gzip, null);
 				gzip.close();
 				if (out.length() < buf.length())
 					buf = out;
 			} catch (IOException err) {
 				// Most likely caused by overflowing the buffer, meaning
 				// its larger if it were compressed. Don't compress.
 				buf = out;
 			}
 
 			HttpAuthMethod authenticator = null;
 			Collection<Type> ignoreTypes = EnumSet.noneOf(Type.class);
 			// Counts number of repeated authentication attempts using the same
 			// authentication scheme
 			int authAttempts = 1;
 			int redirects = 0;
 			for (;;) {
 				try {
 					// The very first time we will try with the authentication
 					// method used on the initial GET request. This is a hint
 					// only; it may fail. If so, we'll then re-try with proper
 					// 401 handling, going through the available authentication
 					// schemes.
 					openStream();
 					if (buf != out) {
 						conn.setRequestProperty(HDR_CONTENT_ENCODING,
 								ENCODING_GZIP);
 					}
 					conn.setFixedLengthStreamingMode((int) buf.length());
 					try (OutputStream httpOut = conn.getOutputStream()) {
 						buf.writeTo(httpOut, null);
 					}
 
 					final int status = HttpSupport.response(conn);
 					switch (status) {
 					case HttpConnection.HTTP_OK:
 						// We're done.
 						return;
 
 					case HttpConnection.HTTP_NOT_FOUND:
 						throw new NoRemoteRepositoryException(uri,
 								MessageFormat.format(JGitText.get().uriNotFound,
 										conn.getURL()));
 
 					case HttpConnection.HTTP_FORBIDDEN:
 						throw new TransportException(uri,
 								MessageFormat.format(
 										JGitText.get().serviceNotPermitted,
 										baseUrl, serviceName));
 
 					case HttpConnection.HTTP_MOVED_PERM:
 					case HttpConnection.HTTP_MOVED_TEMP:
 					case HttpConnection.HTTP_11_MOVED_TEMP:
 						// SEE_OTHER after a POST doesn't make sense for a git
 						// server, so we don't handle it here and thus we'll
 						// report an error in openResponse() later on.
 						if (http.getFollowRedirects() != HttpRedirectMode.TRUE) {
 							// Let openResponse() issue an error
 							return;
 						}
 						currentUri = redirect(conn.getHeaderField(HDR_LOCATION),
 								'/' + serviceName, redirects++);
 						try {
 							baseUrl = toURL(currentUri);
 						} catch (MalformedURLException e) {
 							throw new TransportException(uri,
 									MessageFormat.format(
 											JGitText.get().invalidRedirectLocation,
 											baseUrl, currentUri),
 									e);
 						}
 						continue;
 
 					case HttpConnection.HTTP_UNAUTHORIZED:
 						HttpAuthMethod nextMethod = HttpAuthMethod
 								.scanResponse(conn, ignoreTypes);
 						switch (nextMethod.getType()) {
 						case NONE:
 							throw new TransportException(uri,
 									MessageFormat.format(
 											JGitText.get().authenticationNotSupported,
 											conn.getURL()));
 						case NEGOTIATE:
 							// RFC 4559 states "When using the SPNEGO [...] with
 							// [...] POST, the authentication should be complete
 							// [...] before sending the user data." So in theory
 							// the initial GET should have been authenticated
 							// already. (Unless there was a redirect?)
 							//
 							// We try this only once:
 							ignoreTypes.add(HttpAuthMethod.Type.NEGOTIATE);
 							if (authenticator != null) {
 								ignoreTypes.add(authenticator.getType());
 							}
 							authAttempts = 1;
 							// We only do the Kerberos part of SPNEGO, which
 							// requires only one attempt. We do *not* to the
 							// NTLM part of SPNEGO; it's a multi-round
 							// negotiation and among other problems it would
 							// be unclear when to stop if no HTTP_OK is
 							// forthcoming. In theory a malicious server
 							// could keep sending requests for another NTLM
 							// round, keeping a client stuck here.
 							break;
 						default:
 							// DIGEST or BASIC. Let's be sure we ignore
 							// NEGOTIATE; if it was available, we have tried it
 							// before.
 							ignoreTypes.add(HttpAuthMethod.Type.NEGOTIATE);
 							if (authenticator == null || authenticator
 									.getType() != nextMethod.getType()) {
 								if (authenticator != null) {
 									ignoreTypes.add(authenticator.getType());
 								}
 								authAttempts = 1;
 							}
 							break;
 						}
 						authMethod = nextMethod;
 						authenticator = nextMethod;
 						CredentialsProvider credentialsProvider = getCredentialsProvider();
 						if (credentialsProvider == null) {
 							throw new TransportException(uri,
 									JGitText.get().noCredentialsProvider);
 						}
 						if (authAttempts > 1) {
 							credentialsProvider.reset(currentUri);
 						}
 						if (3 < authAttempts || !authMethod
 								.authorize(currentUri, credentialsProvider)) {
 							throw new TransportException(uri,
 									JGitText.get().notAuthorized);
 						}
 						authAttempts++;
 						continue;
 
 					default:
 						// Just return here; openResponse() will report an
 						// appropriate error.
 						return;
 					}
 				} catch (SSLHandshakeException e) {
 					handleSslFailure(e);
 					continue; // Re-try
 				}
 			}
 		}
 
 		void openResponse() throws IOException {
 			final int status = HttpSupport.response(conn);
 			if (status != HttpConnection.HTTP_OK) {
 				throw new TransportException(uri, status + " " //$NON-NLS-1$
 						+ conn.getResponseMessage());
 			}
 
 			final String contentType = conn.getContentType();
 			if (!responseType.equals(contentType)) {
 				conn.getInputStream().close();
 				throw wrongContentType(responseType, contentType);
 			}
 		}
 
 		HttpOutputStream getOutputStream() {
 			return out;
 		}
 
 		InputStream getInputStream() {
 			return in;
 		}
 
 		abstract void execute() throws IOException;
 
 		class HttpExecuteStream extends InputStream {
 			@Override
 			public int read() throws IOException {
 				execute();
 				return -1;
 			}
 
 			@Override
 			public int read(byte[] b, int off, int len) throws IOException {
 				execute();
 				return -1;
 			}
 
 			@Override
 			public long skip(long n) throws IOException {
 				execute();
 				return 0;
 			}
 		}
 
 		class HttpOutputStream extends TemporaryBuffer {
 			HttpOutputStream() {
 				super(http.getPostBuffer());
 			}
 
 			@Override
 			protected OutputStream overflow() throws IOException {
 				openStream();
 				conn.setChunkedStreamingMode(0);
 				return conn.getOutputStream();
 			}
 		}
 	}
 
 	/**
 	 * State required to speak multiple HTTP requests with the remote.
 	 * <p>
 	 * A service wrapper provides a normal looking InputStream and OutputStream
 	 * pair which are connected via HTTP to the named remote service. Writing to
 	 * the OutputStream is buffered until either the buffer overflows, or
 	 * reading from the InputStream occurs. If overflow occurs HTTP/1.1 and its
 	 * chunked transfer encoding is used to stream the request data to the
 	 * remote service. If the entire request fits in the memory buffer, the
 	 * older HTTP/1.0 standard and a fixed content length is used instead.
 	 * <p>
 	 * It is an error to attempt to read without there being outstanding data
 	 * ready for transmission on the OutputStream.
 	 * <p>
 	 * No state is preserved between write-read request pairs. The caller is
 	 * responsible for replaying state vector information as part of the request
 	 * data written to the OutputStream. Any session HTTP cookies may or may not
 	 * be preserved between requests, it is left up to the JVM's implementation
 	 * of the HTTP client.
 	 */
 	class MultiRequestService extends Service {
 		boolean finalRequest;
 
 		MultiRequestService(final String serviceName) {
 			super(serviceName);
 		}
 
 		/** Keep opening send-receive pairs to the given URI. */
 		@Override
 		void execute() throws IOException {
 			out.close();
 
 			if (conn == null) {
 				if (out.length() == 0) {
 					// Request output hasn't started yet, but more data is being
 					// requested. If there is no request data buffered and the
 					// final request was already sent, do nothing to ensure the
 					// caller is shown EOF on the InputStream; otherwise an
 					// programming error has occurred within this module.
 					if (finalRequest)
 						return;
 					throw new TransportException(uri,
 							JGitText.get().startingReadStageWithoutWrittenRequestDataPendingIsNotSupported);
 				}
 
 				sendRequest();
 			}
 
 			out.reset();
 
 			openResponse();
 
 			in.add(openInputStream(conn));
 			if (!finalRequest)
 				in.add(execute);
 			conn = null;
 		}
 	}
 
 	/** Service for maintaining a single long-poll connection. */
 	class LongPollService extends Service {
 		/**
 		 * @param serviceName
 		 */
 		LongPollService(String serviceName) {
 			super(serviceName);
 		}
 
 		/** Only open one send-receive request. */
 		@Override
 		void execute() throws IOException {
 			out.close();
 			if (conn == null)
 				sendRequest();
 			openResponse();
 			in.add(openInputStream(conn));
 		}
 	}
 }