第一次使用，随便写写吧！

1. 练习1：在本地仓库修改readme文件，然后通过git提交到github;

• git add .
• git commit -m "RRR" # 提交并备注信息
• git push origin main

2. 练习2：在github上修改readme文件，然后通过git更新到本地仓库

• git fetch origin
• git merge origin/main

3. 练习3：使用pull,等价于fetch+merge

• $ git pull origin/main

# 报错如下：
  fatal: 'origin/main' does not appear to be a git repository
  fatal: Could not read from remote repository.

  Please make sure you have the correct access rights
  and the repository exists.

• $ git pull origin # 成功