Fix RacyGitTests#testRacyGitDetection

This test case assumed file system timestamp resolution of 1 second. On
filesystems with a finer resolution this test fails since the index
entry is only smudged if the file index entry's lastModified and the
lastModified of the git index itself are within the same filesystem
timer tick. Fix this by ensuring that these timestamps are identical
which should work for any filesystem timer resolution.

Bug: 548188
Change-Id: Id84d59e1cfeb48fa008f8f27f2f892c4f73985de
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/RacyGitTests.java

@@ -45,6 +45,7 @@ package org.eclipse.jgit.lib;
 import static java.lang.Long.valueOf;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import java.io.File;
@@ -53,10 +54,12 @@ import java.io.IOException;
 import java.util.TreeSet;
 
 import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.dircache.DirCache;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.eclipse.jgit.treewalk.FileTreeIterator;
 import org.eclipse.jgit.treewalk.FileTreeIteratorWithTimeControl;
 import org.eclipse.jgit.treewalk.NameConflictTreeWalk;
+import org.eclipse.jgit.treewalk.WorkingTreeOptions;
 import org.eclipse.jgit.util.FileUtils;
 import org.junit.Test;
 
@@ -137,8 +140,8 @@ public class RacyGitTests extends RepositoryTestCase {
 		fsTick(db.getIndexFile());
 
 		// create two files
-		File a = addToWorkDir("a", "a");
-		File b = addToWorkDir("b", "b");
+		File a = writeToWorkDir("a", "a");
+		File b = writeToWorkDir("b", "b");
 		assertTrue(a.setLastModified(b.lastModified()));
 		assertTrue(b.setLastModified(b.lastModified()));
 
@@ -158,23 +161,35 @@ public class RacyGitTests extends RepositoryTestCase {
 		fsTick(db.getIndexFile());
 
 		// Create a racy git situation. This is a situation that the index is
-		// updated and then a file is modified within a second. By changing the
-		// index file artificially, we create a fake racy situation.
-		File updatedA = addToWorkDir("a", "a2");
-		assertTrue(updatedA.setLastModified(updatedA.lastModified() + 100));
+		// updated and then a file is modified within the same tick of the
+		// filesystem timestamp resolution. By changing the index file
+		// artificially, we create a fake racy situation.
+		File updatedA = writeToWorkDir("a", "a2");
+		long newLastModified = updatedA.lastModified() + 100;
+		assertTrue(updatedA.setLastModified(newLastModified));
 		resetIndex(new FileTreeIterator(db));
-		assertTrue(db.getIndexFile()
-				.setLastModified(updatedA.lastModified() + 90));
+		assertTrue(db.getIndexFile().setLastModified(newLastModified));
 
-		db.readDirCache();
-		// although racily clean a should not be reported as being dirty
+		DirCache dc = db.readDirCache();
+		// check index state: although racily clean a should not be reported as
+		// being dirty since we forcefully reset the index to match the working
+		// tree
 		assertEquals(
 				"[a, mode:100644, time:t1, smudged, length:0, content:a2]"
 						+ "[b, mode:100644, time:t0, length:1, content:b]",
 				indexState(SMUDGE | MOD_TIME | LENGTH | CONTENT));
+
+		// compare state of files in working tree with index to check that
+		// FileTreeIterator.isModified() works as expected
+		FileTreeIterator f = new FileTreeIterator(db.getWorkTree(), db.getFS(),
+				db.getConfig().get(WorkingTreeOptions.KEY));
+		assertTrue(f.findFile("a"));
+		try (ObjectReader reader = db.newObjectReader()) {
+			assertFalse(f.isModified(dc.getEntry("a"), false, reader));
+		}
 	}
 
-	private File addToWorkDir(String path, String content) throws IOException {
+	private File writeToWorkDir(String path, String content) throws IOException {
 		File f = new File(db.getWorkTree(), path);
 		try (FileOutputStream fos = new FileOutputStream(f)) {
 			fos.write(content.getBytes(UTF_8));