diff --git a/src/main/java/com/google/devtools/build/lib/exec/FilesetManifest.java b/src/main/java/com/google/devtools/build/lib/exec/FilesetManifest.java
new file mode 100644
index 0000000..49865e7
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/exec/FilesetManifest.java
@@ -0,0 +1,184 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.exec;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.common.io.LineProcessor;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.AnalysisUtils;
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
+import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Representation of a Fileset manifest.
+ */
+public final class FilesetManifest {
+  /**
+   * Mode that determines how to handle relative target paths.
+   */
+  public enum RelativeSymlinkBehavior {
+    /** Ignore any relative target paths. */
+    IGNORE,
+
+    /** Give an error if a relative target path is encountered. */
+    ERROR,
+
+    /**
+     * Attempt to locally resolve the relative target path. Consider a manifest with two entries,
+     * foo points to bar, and bar points to the absolute path /foobar. In that case, we can
+     * determine that foo actually points at /foobar. Throw an exception if the local resolution
+     * fails, e.g., if the target is not in the current manifest, or if it points at another
+     * symlink (we could theoretically resolve recursively, but that's more complexity).
+     */
+    RESOLVE;
+  }
+
+  public static FilesetManifest parseManifestFile(
+      Artifact manifest,
+      Path execRoot,
+      String workspaceName,
+      RelativeSymlinkBehavior relSymlinkBehavior)
+          throws IOException {
+    return parseManifestFile(
+        manifest.getExecPath(),
+        execRoot,
+        workspaceName,
+        relSymlinkBehavior);
+  }
+
+  public static FilesetManifest parseManifestFile(
+      PathFragment manifest,
+      Path execRoot,
+      String workspaceName,
+      RelativeSymlinkBehavior relSymlinkBehavior)
+          throws IOException {
+    Path file = execRoot.getRelative(AnalysisUtils.getManifestPathFromFilesetPath(manifest));
+    try {
+      return FileSystemUtils.asByteSource(file).asCharSource(UTF_8)
+          .readLines(
+              new ManifestLineProcessor(workspaceName, manifest, relSymlinkBehavior));
+    } catch (IllegalStateException e) {
+      // We can't throw IOException from getResult below, so we instead use an unchecked exception,
+      // and convert it to an IOException here.
+      throw new IOException(e.getMessage(), e);
+    }
+  }
+
+  private static final class ManifestLineProcessor implements LineProcessor<FilesetManifest> {
+    private final String workspaceName;
+    private final PathFragment targetPrefix;
+    private final RelativeSymlinkBehavior relSymlinkBehavior;
+
+    private int lineNum;
+    private final Map<PathFragment, String> entries = new LinkedHashMap<>();
+    private final Map<PathFragment, String> relativeLinks = new HashMap<>();
+
+    ManifestLineProcessor(
+        String workspaceName,
+        PathFragment targetPrefix,
+        RelativeSymlinkBehavior relSymlinkBehavior) {
+      this.workspaceName = workspaceName;
+      this.targetPrefix = targetPrefix;
+      this.relSymlinkBehavior = relSymlinkBehavior;
+    }
+
+    @Override
+    public boolean processLine(String line) throws IOException {
+      if (++lineNum % 2 == 0) {
+        // Digest line, skip.
+        return true;
+      }
+      if (line.isEmpty()) {
+        return true;
+      }
+
+      String artifact;
+      PathFragment location;
+      int pos = line.indexOf(' ');
+      if (pos == -1) {
+        location = PathFragment.create(line);
+        artifact = null;
+      } else {
+        location = PathFragment.create(line.substring(0, pos));
+        String targetPath = line.substring(pos + 1);
+        artifact = targetPath.isEmpty() ? null : targetPath;
+
+        if (!workspaceName.isEmpty()) {
+          if (!location.getSegment(0).equals(workspaceName)) {
+            throw new IOException(
+                String.format(
+                    "fileset manifest line must start with '%s': '%s'", workspaceName, location));
+          } else {
+            // Erase "<workspaceName>/" prefix.
+            location = location.subFragment(1, location.segmentCount());
+          }
+        }
+      }
+
+      PathFragment fullLocation = targetPrefix.getRelative(location);
+      if (!entries.containsKey(fullLocation)) {
+        boolean isRelativeSymlink = artifact != null && !artifact.startsWith("/");
+        if (isRelativeSymlink && relSymlinkBehavior.equals(RelativeSymlinkBehavior.ERROR)) {
+          throw new IOException(String.format("runfiles target is not absolute: %s", artifact));
+        }
+        if (!isRelativeSymlink
+            || relSymlinkBehavior.equals(RelativeSymlinkBehavior.RESOLVE)) {
+          entries.put(fullLocation, artifact);
+          if (artifact != null && !artifact.startsWith("/")) {
+            relativeLinks.put(fullLocation, artifact);
+          }
+        }
+      }
+      return true;
+    }
+
+    @Override
+    public FilesetManifest getResult() {
+      // Resolve relative symlinks if possible. Note that relativeLinks only contains entries in
+      // RESOLVE mode.
+      for (Map.Entry<PathFragment, String> e : relativeLinks.entrySet()) {
+        PathFragment location = e.getKey();
+        String value = e.getValue();
+        PathFragment actualLocation = location.getParentDirectory().getRelative(value);
+        String actual = entries.get(actualLocation);
+        boolean isActualAcceptable = actual == null || actual.startsWith("/");
+        if (!entries.containsKey(actualLocation) || !isActualAcceptable) {
+          throw new IllegalStateException(
+              String.format(
+                  "runfiles target '%s' is not absolute, and could not be resolved in the same "
+                  + "Fileset", value));
+        }
+        entries.put(location, actual);
+      }
+      return new FilesetManifest(entries);
+    }
+  }
+
+  private final Map<PathFragment, String> entries;
+
+  private FilesetManifest(Map<PathFragment, String> entries) {
+    this.entries = Collections.unmodifiableMap(entries);
+  }
+
+  public Map<PathFragment, String> getEntries() {
+    return entries;
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java b/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
index 1bd4bf4..f30209d 100644
--- a/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
+++ b/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
@@ -13,11 +13,10 @@
 // limitations under the License.
 package com.google.devtools.build.lib.exec;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
+import static com.google.devtools.build.lib.exec.FilesetManifest.RelativeSymlinkBehavior.ERROR;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
-import com.google.common.io.LineProcessor;
 import com.google.devtools.build.lib.actions.ActionInput;
 import com.google.devtools.build.lib.actions.ActionInputFileCache;
 import com.google.devtools.build.lib.actions.ActionInputHelper;
@@ -25,10 +24,7 @@
 import com.google.devtools.build.lib.actions.Artifact.ArtifactExpander;
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.actions.Spawn;
-import com.google.devtools.build.lib.analysis.AnalysisUtils;
 import com.google.devtools.build.lib.rules.fileset.FilesetActionContext;
-import com.google.devtools.build.lib.vfs.FileSystemUtils;
-import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import java.io.IOException;
 import java.util.List;
@@ -112,71 +108,13 @@
   void parseFilesetManifest(
       Map<PathFragment, ActionInput> inputMappings, Artifact manifest, String workspaceName)
           throws IOException {
-    Path file = manifest.getRoot().getPath().getRelative(
-        AnalysisUtils.getManifestPathFromFilesetPath(
-            manifest.getRootRelativePath()).getPathString());
-    FileSystemUtils.asByteSource(file).asCharSource(UTF_8)
-        .readLines(new ManifestLineProcessor(inputMappings, workspaceName, manifest.getExecPath()));
-  }
-
-  private final class ManifestLineProcessor implements LineProcessor<Object> {
-    private final Map<PathFragment, ActionInput> inputMap;
-    private final String workspaceName;
-    private final PathFragment targetPrefix;
-    private int lineNum = 0;
-
-    ManifestLineProcessor(
-        Map<PathFragment, ActionInput> inputMap,
-        String workspaceName,
-        PathFragment targetPrefix) {
-      this.inputMap = inputMap;
-      this.workspaceName = workspaceName;
-      this.targetPrefix = targetPrefix;
-    }
-
-    @Override
-    public boolean processLine(String line) throws IOException {
-      if (++lineNum % 2 == 0) {
-        // Digest line, skip.
-        return true;
-      }
-      if (line.isEmpty()) {
-        return true;
-      }
-
-      ActionInput artifact;
-      PathFragment location;
-      int pos = line.indexOf(' ');
-      if (pos == -1) {
-        location = PathFragment.create(line);
-        artifact = EMPTY_FILE;
-      } else {
-        String targetPath = line.substring(pos + 1);
-        if (targetPath.charAt(0) != '/') {
-          throw new IOException(String.format("runfiles target is not absolute: %s", targetPath));
-        }
-        artifact = targetPath.isEmpty() ? EMPTY_FILE : ActionInputHelper.fromPath(targetPath);
-
-        location = PathFragment.create(line.substring(0, pos));
-        if (!workspaceName.isEmpty()) {
-          if (!location.getSegment(0).equals(workspaceName)) {
-            throw new IOException(
-                String.format(
-                    "fileset manifest line must start with '%s': '%s'", workspaceName, location));
-          } else {
-            // Erase "<workspaceName>/".
-            location = location.subFragment(1, location.segmentCount());
-          }
-        }
-      }
-
-      addMapping(inputMap, targetPrefix.getRelative(location), artifact);
-      return true;
-    }
-
-    @Override
-    public Object getResult() {
-      return null; // Unused.
+    FilesetManifest filesetManifest =
+        FilesetManifest.parseManifestFile(
+            manifest, manifest.getRoot().getExecRoot(), workspaceName, ERROR);
+    for (Map.Entry<PathFragment, String> mapping : filesetManifest.getEntries().entrySet()) {
+      String value = mapping.getValue();
+      ActionInput artifact = value == null ? EMPTY_FILE : ActionInputHelper.fromPath(value);
+      addMapping(inputMappings, mapping.getKey(), artifact);
     }
   }