Optimize SequenceGlob matching performance using a Set.

When `origin_files` is provided as a list of files, Copybara uses `SequenceGlob`.
Previously, `SequenceGlob.relativeTo` returned a `PathMatcher` that iterated linearly through all files in the list for every file checked during checkout. This resulted in O(N*M) complexity where N is the number of files in the list and M is the number of files checked.

This change optimizes `SequenceGlob` to pre-calculate the relative paths and store them in an `ImmutableSet`. This allows for O(1) lookup time during matching, reducing the complexity to O(N + M).

Benchmarks show a ~73x speedup in matching time for 5000 files (1589ms -> 21ms).

BUG=467397947
GWSQ_IGNORE: chriscampos@google.com
PiperOrigin-RevId: 847778127
Change-Id: Idaf21e5773faa3d61ce3c9a07ac0d1524df1c0f5

Author: chris-campos

java/com/google/copybara/util/SequenceGlob.java

@@ -16,10 +16,10 @@
 
 package com.google.copybara.util;
 
-import static com.google.common.collect.ImmutableList.toImmutableList;
-
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import com.google.copybara.util.GlobAtom.AtomType;
+import java.nio.file.FileSystem;
 import java.nio.file.Path;
 import java.nio.file.PathMatcher;
 import net.starlark.java.eval.EvalException;
@@ -38,13 +38,40 @@ String toStringWithParentheses(boolean isRootGlob) {
   }
 
   @Override
-  public PathMatcher relativeTo(Path path) {
+  public PathMatcher relativeTo(Path root) {
+    ImmutableSet.Builder<Path> paths = ImmutableSet.builder();
+    for (GlobAtom atom : include) {
+      paths.add(resolvePath(root, atom.pattern()));
+    }
+    final ImmutableSet<Path> matchPaths = paths.build();
     return new ReadablePathMatcher(
-        FileUtil.anyPathMatcher(
-            include.stream().map(g -> g.matcher(path)).collect(toImmutableList())),
+        new PathMatcher() {
+          @Override
+          public boolean matches(Path path) {
+            return matchPaths.contains(path.normalize());
+          }
+
+          @Override
+          public String toString() {
+            return SequenceGlob.this.toString();
+          }
+        },
         this.toString());
   }
 
+  private Path resolvePath(Path root, String pattern) {
+    // Logic from GlobAtom.SINGLE_FILE.matcher
+    FileSystem fs = root.getFileSystem();
+    String rootStr = root.normalize().toString();
+    String separator = fs.getSeparator();
+
+    if (!rootStr.endsWith(separator)) {
+      rootStr += separator;
+    }
+
+    return fs.getPath(rootStr + pattern);
+  }
+
   public static SequenceGlob ofStarlarkList(StarlarkList<?> patterns) throws EvalException {
     ImmutableList.Builder<GlobAtom> atoms = ImmutableList.builder();
     for (Object pattern : patterns) {