UploadPack: Use reachable-sha1-in-want configuration

C git 2.5 supports setting the equivalent of
RequestPolicy.REACHABLE_COMMIT with uploadpack.allowreachablesha1inwant.
Parse this into TransportConfig and use it from UploadPack. An explicitly
set RequestPolicy overrides the config, and the policy may still be
upgraded on a unidirectional connection to avoid races.

Change-Id: Id39771a6e42d8082099acde11249306828a053c0
Signed-off-by: Fredrik Medley <fredrik.medley@gmail.com>

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

@@ -193,6 +193,13 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 	 */
 	public static final String OPTION_ALLOW_TIP_SHA1_IN_WANT = GitProtocolConstants.OPTION_ALLOW_TIP_SHA1_IN_WANT;
 
+	/**
+	 * The client supports fetching objects that are reachable from a tip of a
+	 * ref that is allowed to fetch.
+	 * @since 4.1
+	 */
+	public static final String OPTION_ALLOW_REACHABLE_SHA1_IN_WANT = GitProtocolConstants.OPTION_ALLOW_REACHABLE_SHA1_IN_WANT;
+
 	private final RevWalk walk;
 
 	/** All commits that are immediately reachable by a local ref. */

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

@@ -129,6 +129,14 @@ public class GitProtocolConstants {
 	 */
 	public static final String OPTION_ALLOW_TIP_SHA1_IN_WANT = "allow-tip-sha1-in-want"; //$NON-NLS-1$
 
+	/**
+	 * The client supports fetching objects that are reachable from a tip of a
+	 * ref that is allowed to fetch.
+	 *
+	 * @since 4.1
+	 */
+	public static final String OPTION_ALLOW_REACHABLE_SHA1_IN_WANT = "allow-reachable-sha1-in-want"; //$NON-NLS-1$
+
 	/**
 	 * Symbolic reference support for better negotiation.
 	 *

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

@@ -71,6 +71,7 @@ public class TransferConfig {
 	private final boolean safeForWindows;
 	private final boolean safeForMacOS;
 	private final boolean allowTipSha1InWant;
+	private final boolean allowReachableSha1InWant;
 	private final String[] hideRefs;
 
 	TransferConfig(final Repository db) {
@@ -94,6 +95,8 @@ public class TransferConfig {
 
 		allowTipSha1InWant = rc.getBoolean(
 				"uploadpack", "allowtipsha1inwant", false); //$NON-NLS-1$ //$NON-NLS-2$
+		allowReachableSha1InWant = rc.getBoolean(
+				"uploadpack", "allowreachablesha1inwant", false); //$NON-NLS-1$ //$NON-NLS-2$
 		hideRefs = rc.getStringList("uploadpack", null, "hiderefs"); //$NON-NLS-1$ //$NON-NLS-2$
 	}
 
@@ -120,6 +123,14 @@ public class TransferConfig {
 		return allowTipSha1InWant;
 	}
 
+	/**
+	 * @return allow clients to request non-tip SHA-1s?
+	 * @since 4.1
+	 */
+	public boolean isAllowReachableSha1InWant() {
+		return allowReachableSha1InWant;
+	}
+
 	/**
 	 * @return {@link RefFilter} respecting configured hidden refs.
 	 * @since 3.1

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

@@ -46,6 +46,7 @@ package org.eclipse.jgit.transport;
 import static org.eclipse.jgit.lib.RefDatabase.ALL;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_AGENT;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_ALLOW_TIP_SHA1_IN_WANT;
+import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_ALLOW_REACHABLE_SHA1_IN_WANT;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_INCLUDE_TAG;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_MULTI_ACK;
 import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_MULTI_ACK_DETAILED;
@@ -552,8 +553,13 @@ public class UploadPack {
 	 */
 	public void setTransferConfig(TransferConfig tc) {
 		this.transferConfig = tc != null ? tc : new TransferConfig(db);
-		setRequestPolicy(transferConfig.isAllowTipSha1InWant()
-				? RequestPolicy.TIP : RequestPolicy.ADVERTISED);
+		if (transferConfig.isAllowTipSha1InWant()) {
+			setRequestPolicy(transferConfig.isAllowReachableSha1InWant()
+				? RequestPolicy.REACHABLE_COMMIT_TIP : RequestPolicy.TIP);
+		} else {
+			setRequestPolicy(transferConfig.isAllowReachableSha1InWant()
+				? RequestPolicy.REACHABLE_COMMIT : RequestPolicy.ADVERTISED);
+		}
 	}
 
 	/** @return the configured logger. */
@@ -808,6 +814,10 @@ public class UploadPack {
 				|| policy == RequestPolicy.REACHABLE_COMMIT_TIP
 				|| policy == null)
 			adv.advertiseCapability(OPTION_ALLOW_TIP_SHA1_IN_WANT);
+		if (policy == RequestPolicy.REACHABLE_COMMIT
+				|| policy == RequestPolicy.REACHABLE_COMMIT_TIP
+				|| policy == null)
+			adv.advertiseCapability(OPTION_ALLOW_REACHABLE_SHA1_IN_WANT);
 		adv.advertiseCapability(OPTION_AGENT, UserAgent.get());
 		adv.setDerefTags(true);
 		Map<String, Ref> advertisedOrDefaultRefs = getAdvertisedOrDefaultRefs();