Teach UploadPack to support filtering by blob size

Teach UploadPack to advertise the filter capability and support a
"filter" line in the request, accepting blob sizes only, if the
configuration variable "uploadpack.allowfilter" is true. This feature is
currently in the "master" branch of Git, and as of the time of writing,
this feature is to be released in Git 2.17.

This is incomplete in that the filter-by-sparse-specification feature
also supported by Git is not included in this patch.

If a JGit server were to be patched with this commit, and a repository
on that server configured with RequestPolicy.ANY or
RequestPolicy.REACHABLE_COMMIT_TIP, a Git client built from the "master"
branch would be able to perform a partial clone.

Change-Id: If72b4b422c06ab432137e9e5272d353b14b73259
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
index 1383045031..0de9dfd7e2 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
@@ -200,6 +200,13 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 	 */
 	public static final String OPTION_ALLOW_REACHABLE_SHA1_IN_WANT = GitProtocolConstants.OPTION_ALLOW_REACHABLE_SHA1_IN_WANT;
 
+	/**
+	 * The client specified a filter expression.
+	 *
+	 * @since 5.0
+	 */
+	public static final String OPTION_FILTER = GitProtocolConstants.OPTION_FILTER;
+
 	private final RevWalk walk;
 
 	/** All commits that are immediately reachable by a local ref. */
@@ -242,6 +249,9 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 
 	private PacketLineOut pckState;
 
+	/** If not -1, the maximum blob size to be sent to the server. */
+	private final long filterBlobLimit;
+
 	/**
 	 * Create a new connection to fetch using the native git transport.
 	 *
@@ -262,6 +272,7 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 		}
 		includeTags = transport.getTagOpt() != TagOpt.NO_TAGS;
 		thinPack = transport.isFetchThin();
+		filterBlobLimit = transport.getFilterBlobLimit();
 
 		if (local != null) {
 			walk = new RevWalk(local);
@@ -524,6 +535,11 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 		if (first) {
 			return false;
 		}
+		if (filterBlobLimit == 0) {
+			p.writeString(OPTION_FILTER + " blob:none");
+		} else if (filterBlobLimit > 0) {
+			p.writeString(OPTION_FILTER + " blob:limit=" + filterBlobLimit);
+		}
 		p.end();
 		outNeedsEnd = false;
 		return true;
@@ -564,6 +580,11 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 					OPTION_MULTI_ACK_DETAILED));
 		}
 
+		if (filterBlobLimit >= 0 && !wantCapability(line, OPTION_FILTER)) {
+			throw new PackProtocolException(uri,
+					JGitText.get().filterRequiresCapability);
+		}
+
 		addUserAgentCapability(line);
 		return line.toString();
 	}