Add support to follow HTTP redirects

git-core follows HTTP redirects so JGit should also provide this.

Implement config setting http.followRedirects with possible values
"false" (= never), "true" (= always), and "initial" (only on GET, but
not on POST).[1]

We must do our own redirect handling and cannot rely on the support
that the underlying real connection may offer. At least the JDK's
HttpURLConnection has two features that get in the way:

* it does not allow cross-protocol redirects and thus fails on
  http->https redirects (for instance, on Github).
* it translates a redirect after a POST to a GET unless the system
  property "http.strictPostRedirect" is set to true. We don't want
  to manipulate that system setting nor require it.

Additionally, git has its own rules about what redirects it accepts;[2]
for instance, it does not allow a redirect that adds query arguments.

We handle response codes 301, 302, 303, and 307 as per RFC 2616.[3]
On POST we do not handle 303, and we follow redirects only if
http.followRedirects == true.

Redirects are followed only a certain number of times. There are two
ways to control that limit:

* by default, the limit is given by the http.maxRedirects system
  property that is also used by the JDK. If the system property is
  not set, the default is 5. (This is much lower than the JDK default
  of 20, but I don't see the value of following so many redirects.)
* this can be overwritten by a http.maxRedirects git config setting.

The JGit http.* git config settings are currently all global; JGit has
no support yet for URI-specific settings "http.<pattern>.name". Adding
support for that is well beyond the scope of this change.

Like git-core, we log every redirect attempt (LOG.info) so that users
may know about the redirection having occurred.

Extends the test framework to configure an AppServer with HTTPS support
so that we can test cloning via HTTPS and redirections involving HTTPS.

[1] https://git-scm.com/docs/git-config
[2] https://kernel.googlesource.com/pub/scm/git/git/+/6628eb41db5189c0cdfdced6d8697e7c813c5f0f
[3] https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

CQ: 13987
Bug: 465167
Change-Id: I86518cb76842f7d326b51f8715e3bbf8ada89859
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

1 files changed, 85 insertions, 0 deletions

diff --git a/org.eclipse.jgit.http.test/src/org/eclipse/jgit/http/test/TestRepositoryResolver.java b/org.eclipse.jgit.http.test/src/org/eclipse/jgit/http/test/TestRepositoryResolver.java
new file mode 100644
index 0000000000..334e57c6d1
--- /dev/null
+++ b/org.eclipse.jgit.http.test/src/org/eclipse/jgit/http/test/TestRepositoryResolver.java
@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2016, 2017 Google Inc.
+ * 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.http.test;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.transport.resolver.RepositoryResolver;
+import org.eclipse.jgit.transport.resolver.ServiceNotEnabledException;
+
+/** A simple repository resolver for tests. */
+public final class TestRepositoryResolver
+		implements RepositoryResolver<HttpServletRequest> {
+
+	private final TestRepository<Repository> repo;
+
+	private final String repoName;
+
+	/**
+	 * Creates a new {@link TestRepositoryResolver} that resolves the given name to
+	 * the given repository.
+	 *
+	 * @param repo
+	 *            to resolve to
+	 * @param repoName
+	 *            to match
+	 */
+	public TestRepositoryResolver(TestRepository<Repository> repo, String repoName) {
+		this.repo = repo;
+		this.repoName = repoName;
+	}
+
+	@Override
+	public Repository open(HttpServletRequest req, String name)
+			throws RepositoryNotFoundException, ServiceNotEnabledException {
+		if (!name.equals(repoName)) {
+			throw new RepositoryNotFoundException(name);
+		}
+		Repository db = repo.getRepository();
+		db.incrementOpen();
+		return db;
+	}
+}