SLCORE-1142 Improve Git blaming for the analysis

backend/commons/src/main/java/org/sonarsource/sonarlint/core/commons/util/git/GitUtils.java

@@ -67,6 +67,7 @@ public class GitUtils {
   private static final String MINIMUM_REQUIRED_GIT_VERSION = "2.24.0";
   private static final Pattern whitespaceRegex = Pattern.compile("\\s+");
   private static final Pattern semanticVersionDelimiter = Pattern.compile("\\.");
+  private static final String BLAME_HISTORY_WINDOW = "--since='6 months ago'";
 
   // So we only have to make the expensive call once (or at most twice) to get the native Git executable!
   private static boolean checkedForNativeGitExecutable = false;
@@ -103,7 +104,7 @@ public static SonarLintBlameResult getBlameResult(Path projectBaseDir, Set<Path>
     return getBlameResult(projectBaseDir, projectBaseRelativeFilePaths, fileContentProvider, GitUtils::checkIfEnabled);
   }
 
-  public static SonarLintBlameResult getBlameResult(Path projectBaseDir, Set<Path> projectBaseRelativeFilePaths, @Nullable UnaryOperator<String> fileContentProvider,
+  static SonarLintBlameResult getBlameResult(Path projectBaseDir, Set<Path> projectBaseRelativeFilePaths, @Nullable UnaryOperator<String> fileContentProvider,
     Predicate<Path> isEnabled) {
     if (isEnabled.test(projectBaseDir)) {
       LOG.debug("Using native git blame");
@@ -201,7 +202,7 @@ public static SonarLintBlameResult blameFromNativeCommand(Path projectBaseDir, S
       for (var relativeFilePath : projectBaseRelativeFilePaths) {
         try {
           return parseBlameOutput(executeGitCommand(projectBaseDir,
-              nativeExecutable, "blame", projectBaseDir.resolve(relativeFilePath).toString(), "--line-porcelain", "--encoding=UTF-8"),
+              nativeExecutable, "blame", BLAME_HISTORY_WINDOW, projectBaseDir.resolve(relativeFilePath).toString(), "--line-porcelain", "--encoding=UTF-8"),
             projectBaseDir.resolve(relativeFilePath).toString().replace("\\", "/"), projectBaseDir);
         } catch (IOException e) {
           throw new IllegalStateException("Failed to blame repository files", e);

backend/commons/src/test/java/org/sonarsource/sonarlint/core/commons/util/git/GitUtilsTest.java

@@ -23,10 +23,13 @@
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.time.temporal.ChronoUnit;
+import java.util.Calendar;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.TimeZone;
 import java.util.function.UnaryOperator;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
@@ -55,9 +58,11 @@
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.sonarsource.sonarlint.core.commons.testutils.GitUtils.addFileToGitIgnoreAndCommit;
 import static org.sonarsource.sonarlint.core.commons.testutils.GitUtils.commit;
+import static org.sonarsource.sonarlint.core.commons.testutils.GitUtils.commitAtDate;
 import static org.sonarsource.sonarlint.core.commons.testutils.GitUtils.createFile;
 import static org.sonarsource.sonarlint.core.commons.testutils.GitUtils.createRepository;
 import static org.sonarsource.sonarlint.core.commons.testutils.GitUtils.modifyFile;
+import static org.sonarsource.sonarlint.core.commons.util.git.GitUtils.blameFromNativeCommand;
 import static org.sonarsource.sonarlint.core.commons.util.git.GitUtils.blameWithFilesGitCommand;
 import static org.sonarsource.sonarlint.core.commons.util.git.GitUtils.getBlameResult;
 import static org.sonarsource.sonarlint.core.commons.util.git.GitUtils.getVSCChangedFiles;
@@ -350,6 +355,46 @@ void git_blame_works_for_bare_repos_too() {
     assertThat(sonarLintBlameResult.getLatestChangeDateForLinesInFile(Path.of("fileB"), List.of(3))).isEmpty();
   }
 
+  @Test
+  void it_should_blame_file_since_provided_period() throws IOException, GitAPIException {
+    var calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
+    calendar.add(Calendar.YEAR, -1);
+    var fileAStr = "fileA";
+    createFile(projectDirPath, fileAStr, "line1");
+    var yearAgo = calendar.toInstant();
+    // initial commit 1 year ago
+    commitAtDate(git, yearAgo, fileAStr);
+    var lines = new String[3];
+
+    // second commit 4 months after initial commit
+    calendar.add(Calendar.MONTH, 4);
+    lines[0] = "line1";
+    lines[1] = "line2";
+    var eightMonthsAgo = calendar.toInstant();
+    modifyFile(projectDirPath.resolve(fileAStr), lines);
+    commitAtDate(git, eightMonthsAgo, fileAStr);
+
+    // third commit 4 months after second commit
+    calendar.add(Calendar.MONTH, 4);
+    lines[2] = "line3";
+    var fourMonthsAgo = calendar.toInstant();
+    modifyFile(projectDirPath.resolve(fileAStr), lines);
+    commitAtDate(git, fourMonthsAgo, fileAStr);
+    var fileA = Path.of(fileAStr);
+
+    var blameResult = blameFromNativeCommand(projectDirPath, Set.of(fileA));
+
+    var line1Date = blameResult.getLatestChangeDateForLinesInFile(fileA, List.of(1)).get();
+    var line2Date = blameResult.getLatestChangeDateForLinesInFile(fileA, List.of(2)).get();
+    var line3Date = blameResult.getLatestChangeDateForLinesInFile(fileA, List.of(3)).get();
+    // line 1 was committed 1 year ago but should have commit date of the first commit earlier than blame time window - 6 months ago
+    assertThat(ChronoUnit.DAYS.between(line2Date.toInstant(), line1Date.toInstant())).isZero();
+    // line 2 was committed 8 months ago, it's outside the blame time window, but it's a first commit outside the range, so it has real commit date
+    assertThat(ChronoUnit.MINUTES.between(line2Date.toInstant(), eightMonthsAgo)).isZero();
+    // line 3 was committed 4 months ago, it's inside the blame time window, so it has real commit date
+    assertThat(ChronoUnit.MINUTES.between(line3Date.toInstant(), fourMonthsAgo)).isZero();
+  }
+
   private static void setUpBareRepo(Map<String, String> filePathContentMap) throws IOException, GitAPIException {
     bareRepoPath = Files.createTempDirectory("bare-repo");
     workingRepoPath = Files.createTempDirectory("working-repo");