fix(git): keep the merge parent when git_commit concludes a merge

src/git/src/mcp_server_git/server.py

@@ -126,7 +126,15 @@ def git_diff(repo: git.Repo, target: str, context_lines: int = DEFAULT_CONTEXT_L
     return repo.git.diff(f"--unified={context_lines}", target)
 
 def git_commit(repo: git.Repo, message: str) -> str:
-    commit = repo.index.commit(message)
+    # During a merge, keep the merged-in commits as parents and clear the merge state, like `git commit`.
+    merge_head = Path(repo.git_dir) / "MERGE_HEAD"
+    if merge_head.exists():
+        parents = [repo.head.commit, *(repo.commit(sha) for sha in merge_head.read_text().split())]
+        commit = repo.index.commit(message, parent_commits=parents)
+        for name in ("MERGE_HEAD", "MERGE_MSG", "MERGE_MODE"):
+            (Path(repo.git_dir) / name).unlink(missing_ok=True)
+    else:
+        commit = repo.index.commit(message)
     return f"Changes committed successfully with hash {commit.hexsha}"
 
 def git_add(repo: git.Repo, files: list[str]) -> str:

src/git/tests/test_server.py

@@ -236,6 +236,30 @@ def test_git_log_default(test_repository):
     assert len(result) >= 1
     assert "initial commit" in result[0]
 
+def test_git_commit_concludes_a_merge(test_repository):
+    with test_repository.config_writer() as config:
+        config.set_value("user", "name", "Test User")
+        config.set_value("user", "email", "test@example.com")
+    main = test_repository.active_branch
+    test_repository.git.checkout("-b", "feature")
+    Path(test_repository.working_dir, "test.txt").write_text("feature")
+    test_repository.index.add(["test.txt"])
+    feature_commit = test_repository.index.commit("feature change")
+    main.checkout()
+    Path(test_repository.working_dir, "test.txt").write_text("main")
+    test_repository.index.add(["test.txt"])
+    main_commit = test_repository.index.commit("main change")
+    with pytest.raises(git.GitCommandError):
+        test_repository.git.merge("feature")
+
+    Path(test_repository.working_dir, "test.txt").write_text("resolved")
+    test_repository.git.add("test.txt")
+    git_commit(test_repository, "merge feature")
+
+    merge_commit = test_repository.head.commit
+    assert merge_commit.parents == (main_commit, feature_commit)
+    assert not Path(test_repository.git_dir, "MERGE_HEAD").exists()
+
 def test_git_create_branch(test_repository):
     result = git_create_branch(test_repository, "new-feature-branch")