feat: libra add rebase subcommand.

[yyjeqhc]

Part of #1239
实现libra rebase子命令的基本功能
目前效果：
libra rebase main
把当前分支变基到main分支。
初始化仓库：

#!/bin/bash

# =================================================================
#  脚本：Rebase 基础功能测试
# =================================================================

# --- 1. 环境准备 ---
echo "===== SCENARIO: BASIC REBASE TEST ====="
rm -rf *.txt .libra
libra init
echo "✅ Repo initialized."

# --- 2. 创建 master 分支的两个基础提交 ---
echo "content1" > file.txt
libra add file.txt
libra commit -m "C1: Add file.txt on master"
echo "✅ C1: Commit on master."

echo "content2" >> file.txt
libra add file.txt
libra commit -m "C2: Modify file.txt on master"
echo "✅ C2: Commit on master. This will be the common ancestor."

# --- 3. 创建并切换到 feature 分支 ---
# feature 分支从 C2 开始
libra switch -c feature
echo "✅ Switched to new branch 'feature'."

# --- 4. 在 feature 分支上创建两个独有的提交 ---
echo "featureA" > feature_a.txt
libra add feature_a.txt
libra commit -m "F1: Add feature_a.txt on feature branch"
echo "✅ F1: Commit on feature branch."

echo "featureB" > feature_b.txt
libra add feature_b.txt
libra commit -m "F2: Add feature_b.txt on feature branch"
echo "✅ F2: Commit on feature branch."

# --- 5. 切换回 master 分支，并让它前进 ---
libra switch master
echo "✅ Switched back to master."

echo "master_change" > master_only.txt
libra add master_only.txt
libra commit -m "C3: Add master_only.txt on master"
echo "✅ C3: Master branch moved forward."

# --- 6. 显示最终状态 ---
echo
echo "🎉 Rebase test repo is ready. Current state:"
echo "Master and feature have diverged from C2."
echo
libra log

测试：

root@MSI:~/724/2# libra switch feature
root@MSI:~/724/2# ls
feature_a.txt  feature_b.txt  file.txt
root@MSI:~/724/2# libra rebase master
Found common ancestor: 6d9c421
Rebasing 2 commits from 'feature' onto 'master'...
Applied: 3c74626
Applied: c80375f
Successfully rebased branch 'feature' onto 'master'.
root@MSI:~/724/2# ls
feature_a.txt  feature_b.txt  file.txt  master_only.txt
root@MSI:~/724/2# cat file.txt
content1
content2

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
mega	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 27, 2025 4:03pm

[Copilot]

Pull Request Overview

This PR implements the libra rebase subcommand to reapply commits from the current branch on top of another base commit. This basic rebase functionality supports linear rebasing by finding the common ancestor, collecting commits to replay, and applying them sequentially on the new base.

• Adds complete rebase command implementation with three-way merge logic
• Implements comprehensive test coverage for basic rebase scenarios
• Updates CLI interface and documentation for the new rebase functionality

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
libra/src/command/rebase.rs	Core rebase implementation with commit replay, merge base finding, and tree operations
libra/tests/command/rebase_test.rs	Test suite covering basic rebase and up-to-date scenarios
libra/src/command/mod.rs	Module declaration for rebase command
libra/src/cli.rs	CLI integration for rebase subcommand
libra/tests/command/mod.rs	Test module registration
aria/contents/docs/libra/command/rebase/index.mdx	User documentation for rebase command

[Copilot]

The error message should be more descriptive and follow standard Git error format. Consider: 'fatal: cannot rebase initial commit'

Suggested change

	.ok_or_else(|| "commit to replay has no parents".to_string())?;
	.ok_or_else(|| "fatal: cannot rebase initial commit".to_string())?;

[Copilot]

The error message should follow Git's standard format. Consider: 'fatal: ambiguous argument '{reference}': unknown revision or path not in the working tree.'

Suggested change

	Err(_) => Err(format!("invalid reference: {reference}")),
	Err(_) => Err(format!("fatal: ambiguous argument '{reference}': unknown revision or path not in the working tree")),

[Copilot]

The merge base algorithm could be optimized. Consider implementing a more efficient approach using commit timestamps or generation numbers to avoid potentially exploring the entire commit history.

Suggested change

	while !queue1.is_empty() || !queue2.is_empty() {
	while !queue1.is_empty() || !queue2.is_empty() {
	// Sort queues by generation numbers or timestamps
	queue1.sort_by_key(|id| {
	let commit: Commit = load_object(id).map_err(|e| e.to_string()).unwrap();
	commit.generation_number // or commit.timestamp
	});
	queue2.sort_by_key(|id| {
	let commit: Commit = load_object(id).map_err(|e| e.to_string()).unwrap();
	commit.generation_number // or commit.timestamp
	});

[Copilot]

The current implementation lacks conflict detection and resolution, which is essential for production rebase functionality. This could lead to data loss or incorrect merges when conflicts occur.

[Copilot]

Assuming all files are blobs will cause incorrect behavior for executable files, symlinks, and submodules. This could corrupt the repository state during rebase.

Suggested change

	let item = mercury::internal::object::tree::TreeItem {
	mode: mercury::internal::object::tree::TreeItemMode::Blob,
	name: path.file_name().unwrap().to_str().unwrap().to_string(),
	id: *hash,
	};
	// TODO: Handle file modes properly - currently assumes all files are blobs
	let mode = if path.is_file() {
	let metadata = fs::metadata(path).map_err(|e| format!("Failed to read metadata: {}", e))?;
	if metadata.permissions().mode() & 0o111 != 0 {
	mercury::internal::object::tree::TreeItemMode::Executable
	} else {
	mercury::internal::object::tree::TreeItemMode::Blob
	}
	} else if path.is_symlink() {
	mercury::internal::object::tree::TreeItemMode::Symlink
	} else {
	mercury::internal::object::tree::TreeItemMode::Submodule
	};
	let item = mercury::internal::object::tree::TreeItem {
	mode,
	name: path.file_name().unwrap().to_str().unwrap().to_string(),
	id: *hash,
	};

[Copilot]

[nitpick] Test output should use proper logging or assertions instead of println!. Consider removing this print statement or replacing with a proper test assertion.

Suggested change

	println!("Basic rebase test passed successfully!");
	// Test passed successfully: all assertions validated.

[Copilot]

[nitpick] Test output should use proper logging or assertions instead of println!. Consider removing this print statement or replacing with a proper test assertion.

Suggested change

	println!("Already up-to-date rebase test passed!");
	assert!(test::is_branch_up_to_date("feature", "master").await, "Feature branch is not up-to-date with master after rebase.");