diff --git a/org.eclipse.jgit/META-INF/MANIFEST.MF b/org.eclipse.jgit/META-INF/MANIFEST.MF
index ad2a9d381..7d09fd638 100644
--- a/org.eclipse.jgit/META-INF/MANIFEST.MF
+++ b/org.eclipse.jgit/META-INF/MANIFEST.MF
@@ -132,6 +132,7 @@ Export-Package: org.eclipse.jgit.annotations;version="5.3.0",
    org.eclipse.jgit.util,
    org.eclipse.jgit.util.io,
    org.eclipse.jgit.internal.storage.file,
+   org.eclipse.jgit.internal.transport.parser,
    org.eclipse.jgit.lib,
    org.eclipse.jgit.transport.http,
    org.eclipse.jgit.errors,
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/transport/parser/FirstCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/transport/parser/FirstCommand.java
new file mode 100644
index 000000000..0426b17f0
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/transport/parser/FirstCommand.java
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2018, Google LLC.
+ * 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.internal.transport.parser;
+
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptySet;
+import static java.util.Collections.unmodifiableSet;
+import static java.util.stream.Collectors.toSet;
+
+import java.util.Set;
+
+import org.eclipse.jgit.annotations.NonNull;
+
+/**
+ * In a push, the client sends a list of commands. The first command
+ * is special, as it can include a list of capabilities at its end.
+ * <p>
+ * For example:
+ * "oid oid name\0cap1 cap cap3"
+ * <p>
+ * Not to be confused with {@link FirstWant}, nor with the first line
+ * of the reference advertisement parsed by
+ * {@code BasePackConnection.readAdvertisedRefs}.
+ * <p>
+ * This class parses the inputted command line and holds the results:
+ * the actual command line and the capabilities.
+ */
+public final class FirstCommand {
+	private final String line;
+	private final Set<String> capabilities;
+
+	/**
+	 * Parse the first line of a receive-pack request.
+	 *
+	 * @param line
+	 *            line from the client.
+	 * @return an instance of FirstCommand with capabilities parsed out
+	 */
+	@NonNull
+	public static FirstCommand fromLine(String line) {
+		int nul = line.indexOf('\0');
+		if (nul < 0) {
+			return new FirstCommand(line, emptySet());
+		}
+		Set<String> opts =
+				asList(line.substring(nul + 1).split(" ")) //$NON-NLS-1$
+					.stream()
+					.collect(toSet());
+		return new FirstCommand(line.substring(0, nul), unmodifiableSet(opts));
+	}
+
+	private FirstCommand(String line, Set<String> capabilities) {
+		this.line = line;
+		this.capabilities = capabilities;
+	}
+
+	/** @return non-capabilities part of the line. */
+	@NonNull
+	public String getLine() {
+		return line;
+	}
+
+	/** @return capabilities parsed from the line, as an immutable set. */
+	@NonNull
+	public Set<String> getCapabilities() {
+		return capabilities;
+	}
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
index 03763368a..2439d4fab 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
@@ -80,6 +80,7 @@ import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.internal.storage.file.PackLock;
 import org.eclipse.jgit.internal.submodule.SubmoduleValidator;
 import org.eclipse.jgit.internal.submodule.SubmoduleValidator.SubmoduleValidationException;
+import org.eclipse.jgit.internal.transport.parser.FirstCommand;
 import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.BatchRefUpdate;
 import org.eclipse.jgit.lib.Config;
@@ -119,10 +120,14 @@ import org.eclipse.jgit.util.io.TimeoutOutputStream;
  * Subclasses compose these operations into full service implementations.
  */
 public abstract class BaseReceivePack {
-	/** Data in the first line of a request, the line itself plus capabilities. */
+	/**
+	 * Data in the first line of a request, the line itself plus capabilities.
+	 *
+	 * @deprecated Use {@link FirstCommand} instead.
+	 */
+	@Deprecated
 	public static class FirstLine {
-		private final String line;
-		private final Set<String> capabilities;
+		private final FirstCommand command;
 
 		/**
 		 * Parse the first line of a receive-pack request.
@@ -131,25 +136,17 @@ public abstract class BaseReceivePack {
 		 *            line from the client.
 		 */
 		public FirstLine(String line) {
-			final HashSet<String> caps = new HashSet<>();
-			final int nul = line.indexOf('\0');
-			if (nul >= 0) {
-				for (String c : line.substring(nul + 1).split(" ")) //$NON-NLS-1$
-					caps.add(c);
-				this.line = line.substring(0, nul);
-			} else
-				this.line = line;
-			this.capabilities = Collections.unmodifiableSet(caps);
+			command = FirstCommand.fromLine(line);
 		}
 
 		/** @return non-capabilities part of the line. */
 		public String getLine() {
-			return line;
+			return command.getLine();
 		}
 
 		/** @return capabilities parsed from the line. */
 		public Set<String> getCapabilities() {
-			return capabilities;
+			return command.getCapabilities();
 		}
 	}
 
@@ -1310,7 +1307,7 @@ public abstract class BaseReceivePack {
 
 				if (firstPkt) {
 					firstPkt = false;
-					FirstLine firstLine = new FirstLine(line);
+					FirstCommand firstLine = FirstCommand.fromLine(line);
 					enabledCapabilities = firstLine.getCapabilities();
 					line = firstLine.getLine();
 					enableCapabilities();