Add support for reading symrefs from pack capabilities

A SymbolicRef is added to the advertised refs for any symref in
capabilities whose target is an advertised ref; this may replace an
existing entry, such as HEAD.

When cloning, if any advertised HEAD is symbolic then use the target
rather than looking for an advertised ref with a matching objectId.

Add --symref option to LsRemote command.

Bug: 514052
Change-Id: Idfb48e6f6e8dcfe57a6896883fe6d84d533aa9d0
Signed-off-by: Lee Worrall <worrall.la@gmail.com>

1 files changed, 233 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/BasePackConnectionTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/BasePackConnectionTest.java
new file mode 100644
index 0000000000..64b16f659a
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/BasePackConnectionTest.java
@@ -0,0 +1,233 @@
+/*
+ * Copyright (C) 2020, Lee Worrall and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.transport;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.hasKey;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.not;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectIdRef;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.SymbolicRef;
+import org.junit.Test;
+
+public class BasePackConnectionTest {
+
+	@Test
+	public void testExtractSymRefsFromCapabilities() {
+		final Map<String, String> symRefs = BasePackConnection
+				.extractSymRefsFromCapabilities(
+						Arrays.asList("symref=HEAD:refs/heads/main",
+								"symref=refs/heads/sym:refs/heads/other"));
+
+		assertEquals(2, symRefs.size());
+		assertEquals("refs/heads/main", symRefs.get("HEAD"));
+		assertEquals("refs/heads/other", symRefs.get("refs/heads/sym"));
+	}
+
+	@Test
+	public void testUpdateWithSymRefsAdds() {
+		final Ref mainRef = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE,
+				"refs/heads/main", ObjectId.fromString(
+						"0000000000000000000000000000000000000001"));
+
+		final Map<String, Ref> refMap = new HashMap<>();
+		refMap.put(mainRef.getName(), mainRef);
+		refMap.put("refs/heads/other",
+				new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, "refs/heads/other",
+						ObjectId.fromString(
+								"0000000000000000000000000000000000000002")));
+
+		final Map<String, String> symRefs = new HashMap<>();
+		symRefs.put("HEAD", "refs/heads/main");
+
+		BasePackConnection.updateWithSymRefs(refMap, symRefs);
+
+		assertThat(refMap, hasKey("HEAD"));
+		final Ref headRef = refMap.get("HEAD");
+		assertThat(headRef, instanceOf(SymbolicRef.class));
+		final SymbolicRef headSymRef = (SymbolicRef) headRef;
+		assertEquals("HEAD", headSymRef.getName());
+		assertSame(mainRef, headSymRef.getTarget());
+	}
+
+	@Test
+	public void testUpdateWithSymRefsReplaces() {
+		final Ref mainRef = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE,
+				"refs/heads/main", ObjectId.fromString(
+						"0000000000000000000000000000000000000001"));
+
+		final Map<String, Ref> refMap = new HashMap<>();
+		refMap.put(mainRef.getName(), mainRef);
+		refMap.put("HEAD", new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, "HEAD",
+				mainRef.getObjectId()));
+		refMap.put("refs/heads/other",
+				new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, "refs/heads/other",
+						ObjectId.fromString(
+								"0000000000000000000000000000000000000002")));
+
+		final Map<String, String> symRefs = new HashMap<>();
+		symRefs.put("HEAD", "refs/heads/main");
+
+		BasePackConnection.updateWithSymRefs(refMap, symRefs);
+
+		assertThat(refMap, hasKey("HEAD"));
+		final Ref headRef = refMap.get("HEAD");
+		assertThat(headRef, instanceOf(SymbolicRef.class));
+		final SymbolicRef headSymRef = (SymbolicRef) headRef;
+		assertEquals("HEAD", headSymRef.getName());
+		assertSame(mainRef, headSymRef.getTarget());
+	}
+
+	@Test
+	public void testUpdateWithSymRefsWithIndirectsAdds() {
+		final Ref mainRef = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE,
+				"refs/heads/main", ObjectId.fromString(
+						"0000000000000000000000000000000000000001"));
+
+		final Map<String, Ref> refMap = new HashMap<>();
+		refMap.put(mainRef.getName(), mainRef);
+		refMap.put("refs/heads/other",
+				new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, "refs/heads/other",
+						ObjectId.fromString(
+								"0000000000000000000000000000000000000002")));
+
+		final Map<String, String> symRefs = new LinkedHashMap<>(); // Ordered
+		symRefs.put("refs/heads/sym3", "refs/heads/sym2"); // Forward reference
+		symRefs.put("refs/heads/sym1", "refs/heads/main");
+		symRefs.put("refs/heads/sym2", "refs/heads/sym1"); // Backward reference
+
+		BasePackConnection.updateWithSymRefs(refMap, symRefs);
+
+		assertThat(refMap, hasKey("refs/heads/sym1"));
+		final Ref sym1Ref = refMap.get("refs/heads/sym1");
+		assertThat(sym1Ref, instanceOf(SymbolicRef.class));
+		final SymbolicRef sym1SymRef = (SymbolicRef) sym1Ref;
+		assertEquals("refs/heads/sym1", sym1SymRef.getName());
+		assertSame(mainRef, sym1SymRef.getTarget());
+
+		assertThat(refMap, hasKey("refs/heads/sym2"));
+		final Ref sym2Ref = refMap.get("refs/heads/sym2");
+		assertThat(sym2Ref, instanceOf(SymbolicRef.class));
+		final SymbolicRef sym2SymRef = (SymbolicRef) sym2Ref;
+		assertEquals("refs/heads/sym2", sym2SymRef.getName());
+		assertSame(sym1SymRef, sym2SymRef.getTarget());
+
+		assertThat(refMap, hasKey("refs/heads/sym3"));
+		final Ref sym3Ref = refMap.get("refs/heads/sym3");
+		assertThat(sym3Ref, instanceOf(SymbolicRef.class));
+		final SymbolicRef sym3SymRef = (SymbolicRef) sym3Ref;
+		assertEquals("refs/heads/sym3", sym3SymRef.getName());
+		assertSame(sym2SymRef, sym3SymRef.getTarget());
+	}
+
+	@Test
+	public void testUpdateWithSymRefsWithIndirectsReplaces() {
+		final Ref mainRef = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE,
+				"refs/heads/main", ObjectId.fromString(
+						"0000000000000000000000000000000000000001"));
+
+		final Map<String, Ref> refMap = new HashMap<>();
+		refMap.put(mainRef.getName(), mainRef);
+		refMap.put("refs/heads/sym1", new ObjectIdRef.Unpeeled(
+				Ref.Storage.LOOSE, "refs/heads/sym1", mainRef.getObjectId()));
+		refMap.put("refs/heads/sym2", new ObjectIdRef.Unpeeled(
+				Ref.Storage.LOOSE, "refs/heads/sym2", mainRef.getObjectId()));
+		refMap.put("refs/heads/sym3", new ObjectIdRef.Unpeeled(
+				Ref.Storage.LOOSE, "refs/heads/sym3", mainRef.getObjectId()));
+		refMap.put("refs/heads/other",
+				new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, "refs/heads/other",
+						ObjectId.fromString(
+								"0000000000000000000000000000000000000002")));
+
+		final Map<String, String> symRefs = new LinkedHashMap<>(); // Ordered
+		symRefs.put("refs/heads/sym3", "refs/heads/sym2"); // Forward reference
+		symRefs.put("refs/heads/sym1", "refs/heads/main");
+		symRefs.put("refs/heads/sym2", "refs/heads/sym1"); // Backward reference
+
+		BasePackConnection.updateWithSymRefs(refMap, symRefs);
+
+		assertThat(refMap, hasKey("refs/heads/sym1"));
+		final Ref sym1Ref = refMap.get("refs/heads/sym1");
+		assertThat(sym1Ref, instanceOf(SymbolicRef.class));
+		final SymbolicRef sym1SymRef = (SymbolicRef) sym1Ref;
+		assertEquals("refs/heads/sym1", sym1SymRef.getName());
+		assertSame(mainRef, sym1SymRef.getTarget());
+
+		assertThat(refMap, hasKey("refs/heads/sym2"));
+		final Ref sym2Ref = refMap.get("refs/heads/sym2");
+		assertThat(sym2Ref, instanceOf(SymbolicRef.class));
+		final SymbolicRef sym2SymRef = (SymbolicRef) sym2Ref;
+		assertEquals("refs/heads/sym2", sym2SymRef.getName());
+		assertSame(sym1SymRef, sym2SymRef.getTarget());
+
+		assertThat(refMap, hasKey("refs/heads/sym3"));
+		final Ref sym3Ref = refMap.get("refs/heads/sym3");
+		assertThat(sym3Ref, instanceOf(SymbolicRef.class));
+		final SymbolicRef sym3SymRef = (SymbolicRef) sym3Ref;
+		assertEquals("refs/heads/sym3", sym3SymRef.getName());
+		assertSame(sym2SymRef, sym3SymRef.getTarget());
+	}
+
+	@Test
+	public void testUpdateWithSymRefsIgnoresSelfReference() {
+		final Ref mainRef = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE,
+				"refs/heads/main", ObjectId.fromString(
+						"0000000000000000000000000000000000000001"));
+
+		final Map<String, Ref> refMap = new HashMap<>();
+		refMap.put(mainRef.getName(), mainRef);
+		refMap.put("refs/heads/other",
+				new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, "refs/heads/other",
+						ObjectId.fromString(
+								"0000000000000000000000000000000000000002")));
+
+		final Map<String, String> symRefs = new LinkedHashMap<>();
+		symRefs.put("refs/heads/sym1", "refs/heads/sym1");
+
+		BasePackConnection.updateWithSymRefs(refMap, symRefs);
+
+		assertEquals(2, refMap.size());
+		assertThat(refMap, not(hasKey("refs/heads/sym1")));
+	}
+
+	@Test
+	public void testUpdateWithSymRefsIgnoreCircularReference() {
+		final Ref mainRef = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE,
+				"refs/heads/main", ObjectId.fromString(
+						"0000000000000000000000000000000000000001"));
+
+		final Map<String, Ref> refMap = new HashMap<>();
+		refMap.put(mainRef.getName(), mainRef);
+		refMap.put("refs/heads/other",
+				new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, "refs/heads/other",
+						ObjectId.fromString(
+								"0000000000000000000000000000000000000002")));
+
+		final Map<String, String> symRefs = new LinkedHashMap<>();
+		symRefs.put("refs/heads/sym2", "refs/heads/sym1");
+		symRefs.put("refs/heads/sym1", "refs/heads/sym2");
+
+		BasePackConnection.updateWithSymRefs(refMap, symRefs);
+
+		assertEquals(2, refMap.size());
+		assertThat(refMap, not(hasKey("refs/heads/sym1")));
+		assertThat(refMap, not(hasKey("refs/heads/sym2")));
+	}
+}
\ No newline at end of file