要获取Bitbucket文件的更改日志，可以使用Bitbucket的API来实现。以下是使用Python编程语言获取Bitbucket文件更改日志的示例代码：

import requests

def get_file_change_log(username, password, repo_owner, repo_name, file_path):
    # 构建API请求URL
    url = f"https://api.bitbucket.org/2.0/repositories/{repo_owner}/{repo_name}/commits"

    # 构建认证头部
    headers = {
        "Authorization": "Basic " + base64.b64encode(f"{username}:{password}".encode("utf-8")).decode("utf-8")
    }

    # 发送API请求
    response = requests.get(url, headers=headers)

    # 检查API响应
    if response.status_code == 200:
        commits = response.json()["values"]
        for commit in commits:
            # 获取每个提交的详细信息
            commit_hash = commit["hash"]
            commit_date = commit["date"]

            # 获取文件更改信息
            file_changes_url = f"{url}/{commit_hash}/diffstat"
            file_changes_response = requests.get(file_changes_url, headers=headers)

            if file_changes_response.status_code == 200:
                file_changes = file_changes_response.json()["values"]
                for file_change in file_changes:
                    # 如果文件路径匹配，则打印更改信息
                    if file_path == file_change["old"]["path"] or file_path == file_change["new"]["path"]:
                        print(f"Commit: {commit_hash}")
                        print(f"Date: {commit_date}")
                        print(f"Change Type: {file_change['type']}")
                        print(f"Old Path: {file_change['old']['path']}")
                        print(f"New Path: {file_change['new']['path']}")
                        print("-----")

    else:
        print("Failed to fetch file change log")

# 示例用法
get_file_change_log("your_username", "your_password", "repo_owner", "repo_name", "path/to/file.txt")

请确保将示例代码中的your_username、your_password、repo_owner、repo_name和path/to/file.txt替换为实际的Bitbucket凭据和文件路径。此示例代码将打印与指定文件路径相关的提交和更改信息。