[JENKINS-65032] Add option to include merge commits in changelogs

src/main/java/org/jenkinsci/plugins/gitclient/ChangelogCommand.java

@@ -108,6 +108,14 @@ public interface ChangelogCommand extends GitCommand {
      */
     ChangelogCommand max(int n);
 
+    /**
+     * Include merge commits in the changelog.
+     *
+     * @param include a boolean.
+     * @return a {@link org.jenkinsci.plugins.gitclient.ChangelogCommand} object.
+     */
+    ChangelogCommand includeMergeCommits(boolean include);
+
     /**
      * Abort this ChangelogCommand without executing it, close any
      * open resources.  The JGit implementation of changelog

src/main/java/org/jenkinsci/plugins/gitclient/CliGitAPIImpl.java

@@ -1243,15 +1243,10 @@ public void prune(RemoteConfig repository) throws GitException, InterruptedExcep
     @Override
     public ChangelogCommand changelog() {
         return new ChangelogCommand() {
-
-            /** Equivalent to the git-log raw format but using ISO 8601 date format - also prevent to depend on git CLI future changes */
-            public static final String RAW =
-                    "commit %H%ntree %T%nparent %P%nauthor %aN <%aE> %ai%ncommitter %cN <%cE> %ci%n%n%w(0,4,4)%B";
-
             private final List<String> revs = new ArrayList<>();
-
             private Integer n = null;
             private Writer out = null;
+            private boolean includeMergeCommits = false;
 
             @Override
             public ChangelogCommand excludes(String rev) {
@@ -1287,23 +1282,27 @@ public ChangelogCommand max(int n) {
                 return this;
             }
 
+            @Override
+            public ChangelogCommand includeMergeCommits(boolean include) {
+                this.includeMergeCommits = include;
+                return this;
+            }
+
             @Override
             public void abort() {
                 /* No cleanup needed to abort the CliGitAPIImpl ChangelogCommand */
             }
 
             @Override
             public void execute() throws GitException, InterruptedException {
-                ArgumentListBuilder args = new ArgumentListBuilder(gitExe, "whatchanged", "--no-abbrev", "-M");
-                if (isAtLeastVersion(1, 8, 3, 0)) {
-                    args.add("--format=" + RAW);
-                } else {
-                    /* Ancient git versions don't support the required format string, use 'raw' and hope it works */
-                    args.add("--format=raw");
-                }
+                ArgumentListBuilder args =
+                        new ArgumentListBuilder(gitExe, "whatchanged", "--no-abbrev", "-M", "--format=raw");
                 if (n != null) {
                     args.add("-n").add(n);
                 }
+                if (includeMergeCommits) {
+                    args.add("-m");
+                }
                 for (String rev : this.revs) {
                     args.add(rev);
                 }

src/main/java/org/jenkinsci/plugins/gitclient/JGitAPIImpl.java

@@ -62,7 +62,6 @@
 import jenkins.util.SystemProperties;
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang.SystemUtils;
-import org.apache.commons.lang.time.FastDateFormat;
 import org.apache.sshd.common.util.security.SecurityUtils;
 import org.eclipse.jgit.api.AddNoteCommand;
 import org.eclipse.jgit.api.CommitCommand;
@@ -115,6 +114,7 @@
 import org.eclipse.jgit.revwalk.RevSort;
 import org.eclipse.jgit.revwalk.RevTree;
 import org.eclipse.jgit.revwalk.RevWalk;
+import org.eclipse.jgit.revwalk.filter.AndRevFilter;
 import org.eclipse.jgit.revwalk.filter.MaxCountRevFilter;
 import org.eclipse.jgit.revwalk.filter.RevFilter;
 import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
@@ -1263,6 +1263,8 @@ public ChangelogCommand changelog() throws GitException {
             private RevWalk walk = new RevWalk(or);
             private Writer out;
             private boolean hasIncludedRev = false;
+            private boolean includeMergeCommits = false;
+            private Integer maxCount = null;
 
             @Override
             public ChangelogCommand excludes(String rev) throws GitException {
@@ -1313,7 +1315,13 @@ public ChangelogCommand to(Writer w) {
 
             @Override
             public ChangelogCommand max(int n) {
-                walk.setRevFilter(MaxCountRevFilter.create(n));
+                this.maxCount = n;
+                return this;
+            }
+
+            @Override
+            public ChangelogCommand includeMergeCommits(boolean include) {
+                this.includeMergeCommits = include;
                 return this;
             }
 
@@ -1340,18 +1348,28 @@ public void execute() throws GitException {
                 if (out == null) {
                     throw new IllegalStateException(); // Match CliGitAPIImpl
                 }
+                List<RevFilter> filters = new ArrayList<>();
+
+                if (!includeMergeCommits) {
+                    filters.add(RevFilter.NO_MERGES);
+                }
+                if (maxCount != null) {
+                    filters.add(MaxCountRevFilter.create(maxCount));
+                }
+                if (filters.isEmpty()) {
+                    walk.setRevFilter(RevFilter.ALL);
+                } else if (filters.size() == 1) {
+                    walk.setRevFilter(filters.get(0));
+                } else {
+                    walk.setRevFilter(AndRevFilter.create(filters));
+                }
                 try (PrintWriter pw = new PrintWriter(out, false)) {
                     RawFormatter formatter = new RawFormatter();
                     if (!hasIncludedRev) {
                         /* If no rev has been included, assume HEAD */
                         this.includes("HEAD");
                     }
                     for (RevCommit commit : walk) {
-                        // git whatachanged doesn't show the merge commits unless -m is given
-                        if (commit.getParentCount() > 1) {
-                            continue;
-                        }
-
                         formatter.format(commit, null, pw, true);
                     }
                 } catch (IOException e) {
@@ -1388,8 +1406,6 @@ private String statusOf(DiffEntry d) {
             }
         }
 
-        public static final String ISO_8601 = "yyyy-MM-dd'T'HH:mm:ssZ";
-
         /**
          * Formats a commit into the raw format.
          *
@@ -1414,11 +1430,8 @@ void format(RevCommit commit, RevCommit parent, PrintWriter pw, Boolean useRawOu
             for (RevCommit p : commit.getParents()) {
                 pw.printf("parent %s\n", p.name());
             }
-            FastDateFormat iso = FastDateFormat.getInstance(ISO_8601);
-            PersonIdent a = commit.getAuthorIdent();
-            pw.printf("author %s <%s> %s\n", a.getName(), a.getEmailAddress(), iso.format(a.getWhen()));
-            PersonIdent c = commit.getCommitterIdent();
-            pw.printf("committer %s <%s> %s\n", c.getName(), c.getEmailAddress(), iso.format(c.getWhen()));
+            pw.printf("author %s\n", commit.getAuthorIdent().toExternalString());
+            pw.printf("committer %s\n", commit.getCommitterIdent().toExternalString());
 
             // indent commit messages by 4 chars
             String msg = commit.getFullMessage();

src/test/java/org/jenkinsci/plugins/gitclient/GitAPITestUpdate.java

@@ -2038,11 +2038,8 @@ public void testChangelogWithMergeCommitAndMaxLogHistory() throws Exception {
                 .setRevisionToMerge(w.git.getHeadRev(w.repoPath(), "branch-1"))
                 .execute();
 
-        /* JGit handles merge commits in changelog differently than CLI git.  See JENKINS-40023. */
-        int maxlimit = w.git instanceof CliGitAPIImpl ? 1 : 2;
-
         StringWriter writer = new StringWriter();
-        w.git.changelog().max(maxlimit).to(writer).execute();
+        w.git.changelog().max(1).to(writer).execute();
         assertThat(writer.toString(), is(not("")));
     }
 

src/test/java/org/jenkinsci/plugins/gitclient/GitClientTest.java

@@ -3023,6 +3023,125 @@ public void testChangelogFirstLineTruncation() throws Exception {
         assertThat(changelogStringWriter.toString(), containsString(padLinesWithSpaces(commitMessage, 4)));
     }
 
+    /**
+     * Tests changelog with merge commits from branches with linear histories.
+     */
+    @Test
+    public void testChangelogWithMergeCommitsAndLinearHistory() throws Exception {
+        final String branch1 = "changelog-branch-1";
+        final String branch2 = "changelog-branch-2";
+        final String mergeMessage = "Merge " + branch2 + " into " + branch1;
+
+        // Create initial commit first
+        ObjectId initialCommit = commitOneFile();
+
+        // Create first branch with a commit
+        gitClient.branch(branch1);
+        gitClient.checkout().ref(branch1).execute();
+        ObjectId branch1Commit = commitFile("file-1", "content-1", branch1 + "-commit");
+
+        // Create second branch with a commit
+        gitClient.branch(branch2);
+        gitClient.checkout().ref(branch2).execute();
+        ObjectId branch2Commit = commitFile("file-2", "content-2", branch2 + "-commit");
+
+        // Merge branch2 into branch1 with merge commit
+        gitClient.checkout().ref(branch1).execute();
+        MergeCommand mergeCommand = gitClient.merge();
+        mergeCommand.setMessage(mergeMessage);
+        mergeCommand.setGitPluginFastForwardMode(MergeCommand.GitPluginFastForwardMode.NO_FF);
+        mergeCommand.setRevisionToMerge(gitClient.getHeadRev(repoRoot.getAbsolutePath(), branch2));
+        mergeCommand.execute();
+
+        // Get changelog with merge commits included
+        StringWriter writer = new StringWriter();
+        gitClient.changelog().includeMergeCommits(true).to(writer).execute();
+        String changelog = writer.toString();
+
+        assertThat(
+                changelog, containsString("commit " + gitClient.revParse("HEAD").name()));
+        assertThat(changelog, containsString(mergeMessage));
+        assertThat(changelog, containsString("commit " + branch2Commit.name()));
+        assertThat(changelog, containsString("parent " + branch1Commit.name()));
+        assertThat(changelog, containsString(branch1 + "-commit"));
+        assertThat(changelog, containsString(branch2 + "-commit"));
+
+        // Get changelog with merge commits excluded
+        writer = new StringWriter();
+        gitClient.changelog().includeMergeCommits(false).to(writer).execute();
+        changelog = writer.toString();
+
+        assertThat(
+                changelog,
+                not(containsString("commit " + gitClient.revParse("HEAD").name())));
+        assertThat(changelog, not(containsString(mergeMessage)));
+        assertThat(changelog, containsString("commit " + branch2Commit.name()));
+        assertThat(changelog, containsString("parent " + branch1Commit.name()));
+        assertThat(changelog, containsString(branch1 + "-commit"));
+        assertThat(changelog, containsString(branch2 + "-commit"));
+    }
+
+    /**
+     * Tests changelog with merge commits from branches with divergent histories.
+     */
+    @Test
+    public void testChangelogWithMergeCommitsAndDivergentHistory() throws Exception {
+        final String branch1 = "changelog-div-1";
+        final String branch2 = "changelog-div-2";
+        final String mergeMessage = "Merge " + branch2 + " into " + branch1;
+
+        ObjectId initialCommit = commitOneFile();
+
+        // Create first branch with a commit
+        gitClient.branch(branch1);
+        gitClient.checkout().ref(branch1).execute();
+        ObjectId branch1Commit = commitFile("file-1", "content-1", branch1 + "-commit");
+
+        // Create second branch from branch1 and add a commit
+        gitClient.branch(branch2);
+        gitClient.checkout().ref(branch2).execute();
+        ObjectId branch2Commit = commitFile("file-2", "content-2", branch2 + "-commit");
+
+        // Add more commits to branch1
+        gitClient.checkout().ref(branch1).execute();
+        commitFile("file-3", "content-3", branch1 + "-commit");
+        ObjectId branch1FinalCommit = commitFile("file-4", "content-4", branch1 + "-commit");
+
+        // Merge branch2 into branch1
+        MergeCommand mergeCommand = gitClient.merge();
+        mergeCommand.setMessage(mergeMessage);
+        mergeCommand.setGitPluginFastForwardMode(MergeCommand.GitPluginFastForwardMode.NO_FF);
+        mergeCommand.setRevisionToMerge(gitClient.getHeadRev(repoRoot.getAbsolutePath(), branch2));
+        mergeCommand.execute();
+        ObjectId mergeCommit = gitClient.revParse("HEAD");
+
+        // Get changelog with merge commits included
+        StringWriter writer = new StringWriter();
+        gitClient.changelog().includeMergeCommits(true).to(writer).execute();
+        String changelog = writer.toString();
+
+        assertThat(changelog, containsString("commit " + mergeCommit.name()));
+        assertThat(changelog, containsString(mergeMessage));
+        assertThat(changelog, containsString("parent " + branch1FinalCommit.name()));
+        assertThat(changelog, containsString("parent " + branch2Commit.name()));
+        assertThat(changelog, containsString(branch1 + "-commit"));
+        assertThat(changelog, containsString(branch2 + "-commit"));
+
+        // Get changelog with merge commits excluded
+        writer = new StringWriter();
+        gitClient.changelog().includeMergeCommits(false).to(writer).execute();
+        changelog = writer.toString();
+
+        assertThat(changelog, not(containsString("commit " + mergeCommit.name())));
+        assertThat(changelog, not(containsString(mergeMessage)));
+        assertThat(changelog, not(containsString("parent " + branch1FinalCommit.name())));
+        assertThat(changelog, not(containsString("parent " + branch2Commit.name())));
+        assertThat(changelog, containsString("commit " + branch1FinalCommit.name()));
+        assertThat(changelog, containsString("parent " + branch1Commit.name()));
+        assertThat(changelog, containsString(branch1 + "-commit"));
+        assertThat(changelog, containsString(branch2 + "-commit"));
+    }
+
     @Test
     @Issue("JENKINS-55284") // Pull must overwrite existing tags
     public void testFetchOverwritesExistingTags() throws Exception {