Use jgit client library for diff with conflict

scm-core/src/main/java/sonia/scm/repository/spi/DiffCommandRequest.java

@@ -115,7 +115,7 @@ public final class DiffCommandRequest extends FileBaseCommandRequest
     this.ancestorChangeset = ancestorChangeset;
   }
 
-  public void setMergeChangeset(String mergeChangeset) {
+  public void setConflictBranch(String mergeChangeset) {
     this.mergeChangeset = mergeChangeset;
   }
 

scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitDiffCommand.java

@@ -37,12 +37,15 @@ import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.diff.DiffEntry;
 import org.eclipse.jgit.diff.DiffFormatter;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.treewalk.CanonicalTreeParser;
 import sonia.scm.repository.GitWorkdirFactory;
 import sonia.scm.repository.InternalRepositoryException;
 import sonia.scm.repository.Repository;
 import sonia.scm.repository.api.DiffCommandBuilder;
 
 import java.io.IOException;
+import java.util.List;
 
 /**
  *
@@ -61,7 +64,9 @@ public class GitDiffCommand extends AbstractGitCommand implements DiffCommand {
   public DiffCommandBuilder.OutputStreamConsumer getDiffResult(DiffCommandRequest request) throws IOException {
     WorkingCopyCloser closer = new WorkingCopyCloser();
     if (Strings.isNullOrEmpty(request.getMergeChangeset())) {
-      return computeDiff(request, open(), closer);
+      Differ.Diff diff = Differ.diff(open(), request);
+      List<DiffEntry> entries = diff.getEntries();
+      return computeDiff(entries, open(), closer);
     } else {
       return inCloneWithPostponedClose(git -> new GitCloneWorker<DiffCommandBuilder.OutputStreamConsumer>(git) {
         @Override
@@ -77,22 +82,34 @@ public class GitDiffCommand extends AbstractGitCommand implements DiffCommand {
             throw new InternalRepositoryException(context.getRepository(), "could not merge branch " + request.getRevision() + " into " + request.getMergeChangeset(), e);
           }
 
+          CanonicalTreeParser treeParser = new CanonicalTreeParser();
+          ObjectId treeId = git.getRepository().resolve(request.getMergeChangeset() + "^{tree}");
+          return outputStream -> {
+            try (ObjectReader reader = git.getRepository().newObjectReader()) {
+              treeParser.reset(reader, treeId);
+              git
+                .diff()
+                .setOldTree(treeParser)
+                .setOutputStream(outputStream)
+                .call();
               DiffCommandRequest clone = request.clone();
               clone.setRevision(sourceRevision.name());
-          return computeDiff(request, getClone().getRepository(), closer);
+            } catch (GitAPIException e) {
+              throw new InternalRepositoryException(repository, "could not calculate diff", e);
+            }
+          };
         }
       }, workdirFactory, request.getMergeChangeset(), closer);
     }
   }
 
-  private DiffCommandBuilder.OutputStreamConsumer computeDiff(DiffCommandRequest request, org.eclipse.jgit.lib.Repository repository, WorkingCopyCloser closer) throws IOException {
+  private DiffCommandBuilder.OutputStreamConsumer computeDiff(List<DiffEntry> entries, org.eclipse.jgit.lib.Repository repository, WorkingCopyCloser closer) throws IOException {
-    Differ.Diff diff = Differ.diff(repository, request);
 
     return output -> {
       try (DiffFormatter formatter = new DiffFormatter(output)) {
         formatter.setRepository(repository);
 
-        for (DiffEntry e : diff.getEntries()) {
+        for (DiffEntry e : entries) {
           if (!e.getOldId().equals(e.getNewId())) {
             formatter.format(e);
           }

scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitDiffCommand_Merge_Test.java

@@ -12,7 +12,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 public class GitDiffCommand_Merge_Test extends AbstractGitCommandTestBase {
 
   static final String DIFF_HEADER = "diff --git a/Main.java b/Main.java";
-  static final String DIFF_FILE_A_MULTIPLE_REVISIONS = "--- a/Main.java\n" +
+  static final String DIFF_FILE_NO_CONFLICT = "--- a/Main.java\n" +
     "+++ b/Main.java\n" +
     "@@ -1,5 +1,5 @@\n" +
     " class Main {\n" +
@@ -21,6 +21,22 @@ public class GitDiffCommand_Merge_Test extends AbstractGitCommandTestBase {
     "         System.out.println(\"Expect nothing more to happen.\");\n" +
     "         System.out.println(\"This is for demonstration, only.\");\n" +
     "     }\n";
+  static final String DIFF_FILE_CONFLICT = "--- a/Main.java\n" +
+    "+++ b/Main.java\n" +
+    "@@ -1,6 +1,13 @@\n" +
+    "+import java.util.Arrays;\n" +
+    "+\n" +
+    " class Main {\n" +
+    "     public static void main(String[] args) {\n" +
+    "         System.out.println(\"Expect nothing more to happen.\");\n" +
+    "+<<<<<<< HEAD\n" +
+    "         System.out.println(\"This is for demonstration, only.\");\n" +
+    "+=======\n" +
+    "+        System.out.println(\"Parameters:\");\n" +
+    "+        Arrays.stream(args).map(arg -> \"- \" + arg).forEach(System.out::println);\n" +
+    "+>>>>>>> feature/print_args\n" +
+    "     }\n" +
+    " }\n";
 
   @Rule
   public BindTransportProtocolRule transportProtocolRule = new BindTransportProtocolRule();
@@ -30,12 +46,12 @@ public class GitDiffCommand_Merge_Test extends AbstractGitCommandTestBase {
     GitDiffCommand gitDiffCommand = new GitDiffCommand(createContext(), repository, new SimpleGitWorkdirFactory(new WorkdirProvider()));
     DiffCommandRequest diffCommandRequest = new DiffCommandRequest();
     diffCommandRequest.setRevision("feature/rename_variable");
-    diffCommandRequest.setMergeChangeset("integration");
+    diffCommandRequest.setConflictBranch("integration");
     ByteArrayOutputStream output = new ByteArrayOutputStream();
     gitDiffCommand.getDiffResult(diffCommandRequest).accept(output);
     assertThat(output.toString())
       .contains(DIFF_HEADER)
-      .contains(DIFF_FILE_A_MULTIPLE_REVISIONS);
+      .contains(DIFF_FILE_NO_CONFLICT);
   }
 
   @Test
@@ -43,12 +59,12 @@ public class GitDiffCommand_Merge_Test extends AbstractGitCommandTestBase {
     GitDiffCommand gitDiffCommand = new GitDiffCommand(createContext(), repository, new SimpleGitWorkdirFactory(new WorkdirProvider()));
     DiffCommandRequest diffCommandRequest = new DiffCommandRequest();
     diffCommandRequest.setRevision("feature/print_args");
-    diffCommandRequest.setMergeChangeset("integration");
+    diffCommandRequest.setConflictBranch("integration");
     ByteArrayOutputStream output = new ByteArrayOutputStream();
     gitDiffCommand.getDiffResult(diffCommandRequest).accept(output);
     assertThat(output.toString())
       .contains(DIFF_HEADER)
-      .contains(DIFF_FILE_A_MULTIPLE_REVISIONS);
+      .contains(DIFF_FILE_CONFLICT);
   }
 
   @Override