git_diff_branches

Compare changes between two branches in a Git repository to identify differences, enabling clear review and analysis of code updates.

Instructions

Show differences between two branches

Input Schema

TableJSON Schema

Name	Required	Description	Default
`base_branch`	Yes
`compare_branch`	Yes
`repo_path`	Yes

Implementation Reference

src/mcp_server_git/git/operations.py:1150-1209 (handler)

The core handler function git_diff_branches that performs the git diff operation between two specified branches, including branch validation, stat-only mode, truncation for large diffs, and error handling.

def git_diff_branches(
    repo: Repo,
    base_branch: str,
    compare_branch: str,
    stat_only: bool = False,
    max_lines: int | None = None,
) -> str:
    """Show differences between two branches with size limiting options"""
    try:
        # Verify branches exist
        all_branches = [branch.name for branch in repo.branches] + [
            ref.name.split("/")[-1] for ref in repo.remote().refs
        ]

        if base_branch not in all_branches:
            return f"❌ Base branch '{base_branch}' not found"
        if compare_branch not in all_branches:
            return f"❌ Compare branch '{compare_branch}' not found"

        # Build diff command arguments
        diff_range = f"{base_branch}...{compare_branch}"

        if stat_only:
            # Return only file statistics
            diff_output = repo.git.diff("--stat", diff_range)
            if not diff_output.strip():
                return f"No differences between {base_branch} and {compare_branch}"
            return f"Diff statistics between {base_branch} and {compare_branch}:\n{diff_output}"

        # Get full diff
        diff_output = repo.git.diff(diff_range)

        if not diff_output.strip():
            return f"No differences between {base_branch} and {compare_branch}"

        # Apply line limit if specified
        if max_lines and max_lines > 0:
            lines = diff_output.split("\n")
            if len(lines) > max_lines:
                truncated_output = "\n".join(lines[:max_lines])
                truncated_output += (
                    f"\n\n... [Truncated: showing {max_lines} of {len(lines)} lines]"
                )
                truncated_output += "\nUse --stat flag for summary or increase max_lines for more content"
                return truncated_output

        # Check if output is extremely large and warn
        if len(diff_output) > 50000:  # 50KB threshold
            lines_count = len(diff_output.split("\n"))
            warning = f"⚠️  Large diff detected ({lines_count} lines, ~{len(diff_output) // 1000}KB)\n"
            warning += "Consider using stat_only=true for summary or max_lines parameter to limit output\n\n"
            return warning + diff_output

        return diff_output

    except GitCommandError as e:
        return f"❌ Diff failed: {str(e)}"
    except Exception as e:
        return f"❌ Diff error: {str(e)}"

src/mcp_server_git/git/models.py:102-108 (schema)

Pydantic BaseModel defining the input schema/parameters for the git_diff_branches tool.

class GitDiffBranches(BaseModel):
    repo_path: str
    base_branch: str
    compare_branch: str
    stat_only: bool | None = False
    max_lines: int | None = None

src/mcp_server_git/core/handlers.py:116-119 (registration)
Registration of the git_diff_branches handler in the CallToolHandler._get_git_handlers() method, wrapping the core function with error handling and repo validation.
```
"git_diff_branches": self._create_git_handler(
    git_diff_branches,
    requires_repo=True,
    extra_args=["base_branch", "compare_branch"],
```

src/mcp_server_git/core/tools.py:286-292 (registration)

ToolDefinition registration in ToolRegistry.initialize_default_tools(), associating the tool name, schema, and category.

ToolDefinition(
    name=GitTools.DIFF_BRANCHES,
    category=ToolCategory.GIT,
    description="Show differences between two branches",
    schema=GitDiffBranches,
    handler=placeholder_handler,
    requires_repo=True,

src/mcp_server_git/git/__init__.py:36-36 (registration)
Export of the git_diff_branches function from the git module for use in handlers.
```
git_diff_branches,
```

MCP Git Server