Implement git diff fetching and parsing

Author: nikita-tkachenko-datadog

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/git/Diff.java

@@ -0,0 +1,30 @@
+package datadog.trace.civisibility.git;
+
+import java.util.BitSet;
+import java.util.Collections;
+import java.util.Map;
+
+public class Diff {
+
+  public static final Diff EMPTY = new Diff(Collections.emptyMap());
+
+  private final Map<String, BitSet> linesByRelativePath;
+
+  public Diff(Map<String, BitSet> linesByRelativePath) {
+    this.linesByRelativePath = linesByRelativePath;
+  }
+
+  public Map<String, BitSet> getLinesByRelativePath() {
+    return Collections.unmodifiableMap(linesByRelativePath);
+  }
+
+  public boolean contains(String relativePath, int startLine, int endLine) {
+    BitSet lines = linesByRelativePath.get(relativePath);
+    if (lines == null) {
+      return false;
+    }
+
+    int changedLine = lines.nextSetBit(startLine);
+    return changedLine != -1 && changedLine <= endLine;
+  }
+}

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/git/tree/GitClient.java

@@ -7,6 +7,7 @@
 import datadog.trace.api.civisibility.telemetry.CiVisibilityMetricCollector;
 import datadog.trace.api.civisibility.telemetry.tag.Command;
 import datadog.trace.api.civisibility.telemetry.tag.ExitCode;
+import datadog.trace.civisibility.git.Diff;
 import datadog.trace.civisibility.utils.ShellCommandExecutor;
 import datadog.trace.util.Strings;
 import edu.umd.cs.findbugs.annotations.NonNull;
@@ -520,6 +521,36 @@ private Path createTempDirectory() throws IOException {
     }
   }
 
+  /**
+   * Returns Git diff between two commits.
+   *
+   * @param baseCommit Commit SHA or reference (HEAD, branch name, etc) of the base commit
+   * @param targetCommit Commit SHA or reference (HEAD, branch name, etc) of the target commit
+   * @return Diff between two commits
+   * @throws IOException If an error was encountered while writing command input or reading output
+   * @throws TimeoutException If timeout was reached while waiting for Git command to finish
+   * @throws InterruptedException If current thread was interrupted while waiting for Git command to
+   *     finish
+   */
+  public @NonNull Diff getGitDiff(String baseCommit, String targetCommit)
+      throws IOException, TimeoutException, InterruptedException {
+    if (Strings.isNotBlank(baseCommit) && Strings.isNotBlank(targetCommit)) {
+      return executeCommand(
+          Command.DIFF,
+          () ->
+              commandExecutor.executeCommand(
+                  GitDiffParser::parse,
+                  "git",
+                  "diff",
+                  "-U0",
+                  "--word-diff=porcelain",
+                  baseCommit,
+                  targetCommit));
+    } else {
+      return Diff.EMPTY;
+    }
+  }
+
   @Override
   public String toString() {
     return "GitClient{" + repoRoot + "}";

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/git/tree/GitDiffParser.java

@@ -0,0 +1,64 @@
+package datadog.trace.civisibility.git.tree;
+
+import datadog.trace.civisibility.git.Diff;
+import edu.umd.cs.findbugs.annotations.NonNull;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.charset.Charset;
+import java.util.BitSet;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class GitDiffParser {
+
+  private static final Pattern CHANGED_FILE_PATTERN =
+      Pattern.compile("^diff --git a/(?<oldfilename>.+) b/(?<newfilename>.+)$");
+  private static final Pattern CHANGED_LINES_PATTERN =
+      Pattern.compile("^@@ -\\d+(,\\d+)? \\+(?<startline>\\d+)(,(?<count>\\d+))? @@");
+
+  public static @NonNull Diff parse(InputStream input) throws IOException {
+    Map<String, BitSet> linesByRelativePath = new HashMap<>();
+
+    BufferedReader bufferedReader =
+        new BufferedReader(new InputStreamReader(input, Charset.defaultCharset()));
+    String changedFile = null;
+    BitSet changedLines = null;
+
+    String line;
+    while ((line = bufferedReader.readLine()) != null) {
+      Matcher changedFileMatcher = CHANGED_FILE_PATTERN.matcher(line);
+      if (changedFileMatcher.matches()) {
+        if (changedFile != null) {
+          linesByRelativePath.put(changedFile, changedLines);
+        }
+        changedFile = changedFileMatcher.group("newfilename");
+        changedLines = new BitSet();
+
+      } else {
+        Matcher changedLinesMatcher = CHANGED_LINES_PATTERN.matcher(line);
+        while (changedLinesMatcher.find()) {
+          int startLine = Integer.parseInt(changedLinesMatcher.group("startline"));
+          String stringCount = changedLinesMatcher.group("count");
+          int count = stringCount != null ? Integer.parseInt(stringCount) : 1;
+          if (changedLines == null) {
+            throw new IllegalStateException(
+                "Line "
+                    + line
+                    + " contains changed lines information, but no changed file info is available");
+          }
+          changedLines.set(startLine, startLine + count);
+        }
+      }
+    }
+
+    if (changedFile != null) {
+      linesByRelativePath.put(changedFile, changedLines);
+    }
+
+    return new Diff(linesByRelativePath);
+  }
+}

dd-java-agent/agent-ci-visibility/src/test/groovy/datadog/trace/civisibility/TestUtils.groovy

@@ -0,0 +1,14 @@
+package datadog.trace.civisibility
+
+abstract class TestUtils {
+
+  private TestUtils() {}
+
+  static BitSet lines(int ... setBits) {
+    BitSet bitSet = new BitSet()
+    for (int bit : setBits) {
+      bitSet.set(bit)
+    }
+    return bitSet
+  }
+}

dd-java-agent/agent-ci-visibility/src/test/groovy/datadog/trace/civisibility/git/DiffTest.groovy

@@ -0,0 +1,37 @@
+package datadog.trace.civisibility.git
+
+import spock.lang.Specification
+
+import static datadog.trace.civisibility.TestUtils.lines
+
+class DiffTest extends Specification {
+
+  def "test diff contains line interval"() {
+    when:
+    def diff = new Diff(lines)
+
+    then:
+    diff.contains(path, interval[0], interval[1]) == result
+
+    where:
+    lines                                               | path     | interval  | result
+    ["path": lines(10)]                                 | "path-b" | [0, 9999] | false
+    ["path": lines(10)]                                 | "path-b" | [10, 10]  | false
+    ["path": lines(10)]                                 | "path"   | [0, 9999] | true
+    ["path": lines(10)]                                 | "path"   | [10, 10]  | true
+    ["path": lines(10)]                                 | "path"   | [9, 9]    | false
+    ["path": lines(10)]                                 | "path"   | [11, 11]  | false
+    ["path": lines(10)]                                 | "path"   | [9, 11]   | true
+    ["path": lines(10, 11, 13)]                         | "path"   | [9, 11]   | true
+    ["path": lines(10, 11, 13)]                         | "path"   | [12, 12]  | false
+    ["path": lines(10, 11, 13)]                         | "path"   | [12, 14]  | true
+    ["path": lines(10, 11, 13)]                         | "path"   | [9, 14]   | true
+    ["path": lines(10, 11, 12, 13)]                     | "path"   | [9, 11]   | true
+    ["path": lines(10, 11, 12, 13)]                     | "path"   | [9, 14]   | true
+    ["path": lines(10, 11, 12, 13)]                     | "path"   | [11, 12]  | true
+    ["path": lines(10, 11, 12, 13)]                     | "path"   | [12, 14]  | true
+    ["path": lines(10, 11, 12, 13), "path-b": lines()]  | "path-b" | [0, 9999] | false
+    ["path": lines(10, 11, 12, 13), "path-b": lines(8)] | "path-b" | [0, 9999] | true
+    ["path": lines(10, 11, 12, 13), "path-b": lines(8)] | "path-b" | [7, 8]    | true
+  }
+}

dd-java-agent/agent-ci-visibility/src/test/groovy/datadog/trace/civisibility/git/tree/GitClientTest.groovy

@@ -11,6 +11,8 @@ import java.nio.file.Files
 import java.nio.file.Path
 import java.nio.file.Paths
 
+import static datadog.trace.civisibility.TestUtils.lines
+
 class GitClientTest extends Specification {
 
   private static final int GIT_COMMAND_TIMEOUT_MILLIS = 10_000
@@ -301,6 +303,20 @@ class GitClientTest extends Specification {
     gitPackObject.getType() == GitObject.COMMIT_TYPE
   }
 
+  def "test git diff"() {
+    given:
+    givenGitRepo()
+
+    when:
+    def gitClient = givenGitClient()
+    def diff = gitClient.getGitDiff("10599ae3c17d66d642f9f143b1ff3dd236111e2a", "6aaa4085c10d16b63a910043e35dbd35d2ef7f1c")
+
+    then:
+    diff.linesByRelativePath == [
+      "src/Datadog.Trace/Logging/DatadogLogging.cs": lines(26, 32, 91, 95, 159, 160)
+    ]
+  }
+
   private void givenGitRepo() {
     givenGitRepo("ci/git/with_pack/git")
   }

dd-java-agent/agent-ci-visibility/src/test/groovy/datadog/trace/civisibility/git/tree/GitDiffParserTest.groovy

@@ -0,0 +1,32 @@
+package datadog.trace.civisibility.git.tree
+
+import spock.lang.Specification
+
+import static datadog.trace.civisibility.TestUtils.lines
+
+class GitDiffParserTest extends Specification {
+
+  def "test git diff parsing: #filename"() {
+    when:
+    def diff
+    try (def gitDiff = GitDiffParserTest.getResourceAsStream(filename)) {
+      diff = GitDiffParser.parse(gitDiff)
+    }
+
+    then:
+    diff.linesByRelativePath == result
+
+    where:
+    filename              | result
+    "git-diff.txt"        | [
+      "java/maven-junit4/pom.xml": lines(10),
+      "java/maven-junit5/pom.xml": lines(14, 41),
+    ]
+    "larger-git-diff.txt" | [
+      "java/maven-junit5/pom.xml"         : lines(14, 41),
+      "java/maven-junit5/module-a/pom.xml": lines(8, 9, 10, 13, 14, 15, 20, 21, 22, 27, 28, 36, 40),
+      "java/maven-junit5/module-b/pom.xml": lines(),
+      "java/maven-junit4/pom.xml"         : lines(10)
+    ]
+  }
+}

dd-java-agent/agent-ci-visibility/src/test/resources/datadog/trace/civisibility/git/tree/git-diff.txt

@@ -0,0 +1,33 @@
+diff --git a/java/maven-junit4/pom.xml b/java/maven-junit4/pom.xml
+index 6d73cda..2a1f220 100644
+--- a/java/maven-junit4/pom.xml
++++ b/java/maven-junit4/pom.xml
+@@ -10 +10 @@
+
+-<name>java-maven-junit4</name>
++<name>java-maven-junit4-test-project</name>
+~
+diff --git a/java/maven-junit5/pom.xml b/java/maven-junit5/pom.xml
+index 7b92d64..834a61c 100644
+--- a/java/maven-junit5/pom.xml
++++ b/java/maven-junit5/pom.xml
+@@ -14 +14 @@
+
+-<module>module-b</module>
++<module>module-c</module>
+~
+@@ -18,3 +17,0 @@
+-        <maven.compiler.source>8</maven.compiler.source>
+~
+-        <maven.compiler.target>8</maven.compiler.target>
+~
+-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+~
+@@ -34 +30,0 @@
+-            <scope>test</scope>
+~
+@@ -45 +41 @@
+
+-<forkCount>1</forkCount>
++<forkCount>2</forkCount>
+~