TransportHttp: support HTTP response 308 Permanent Redirect

RFC 7538[1] added HTTP response code 308, signifying a permanent
redirect that, contrary to the older 301, does not allow changing
the request method from POST to GET.

[1] https://tools.ietf.org/html/rfc7538

Bug: 560936
Change-Id: Ib65f3a3ed75db51d74d1fe81d4abe6fe92b0ca12
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

org.eclipse.jgit/.settings/.api_filters

+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<component id="org.eclipse.jgit" version="2">
+    <resource path="src/org/eclipse/jgit/transport/http/HttpConnection.java" type="org.eclipse.jgit.transport.http.HttpConnection">
+        <filter id="403767336">
+            <message_arguments>
+                <message_argument value="org.eclipse.jgit.transport.http.HttpConnection"/>
+                <message_argument value="HTTP_11_MOVED_PERM"/>
+            </message_arguments>
+        </filter>
+    </resource>
+</component>

org.eclipse.jgit/src/org/eclipse/jgit/transport/TransportHttp.java

 				case HttpConnection.HTTP_MOVED_PERM:
 				case HttpConnection.HTTP_MOVED_TEMP:
 				case HttpConnection.HTTP_SEE_OTHER:
+				case HttpConnection.HTTP_11_MOVED_PERM:
 				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
 
 					case HttpConnection.HTTP_MOVED_PERM:
 					case HttpConnection.HTTP_MOVED_TEMP:
+					case HttpConnection.HTTP_11_MOVED_PERM:
 					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

org.eclipse.jgit/src/org/eclipse/jgit/transport/http/HttpConnection.java

 	int HTTP_SEE_OTHER = java.net.HttpURLConnection.HTTP_SEE_OTHER;
 
 	/**
-	 * HTTP 1.1 additional MOVED_TEMP status code; value = 307.
+	 * HTTP 1.1 additional "temporary redirect" status code; value = 307.
 	 *
 	 * @see #HTTP_MOVED_TEMP
+	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-6.4.7">RFC
+	 *      7231, section 6.4.7: 307 Temporary Redirect</a>
 	 * @since 4.9
 	 */
 	int HTTP_11_MOVED_TEMP = 307;
 
+	/**
+	 * HTTP 1.1 additional "permanent redirect" status code; value = 308.
+	 *
+	 * @see #HTTP_MOVED_TEMP
+	 * @see <a href="https://tools.ietf.org/html/rfc7538#section-3">RFC 7538,
+	 *      section 3: 308 Permanent Redirect</a>
+	 * @since 5.8
+	 */
+	int HTTP_11_MOVED_PERM = 308;
+
 	/**
 	 * @see HttpURLConnection#HTTP_NOT_FOUND
 	 */