MIT-Missing Semester_Topic 6：Version Control (Git) 练习题

本 Topic 的 MIT 讲解网页（练习题未给解答）

练习一

若还没有 Git 的相关经验，阅读 Pro Git 的前几章或诸如 Learn Git Branching 的相关教程，并在学习的同时从 Git 的数据模型（data model）的角度思考各 Git 命令。

老师非常建议阅读 Pro Git。

练习二

clone 该课程（Missing Semester）网站的仓库，随后：

1. 以图的形式展现其版本历史
2. 运用 git log 加一个参数，找到修改 README.md 的最后一人
3. 运用 git blame 与 git show 得到 _config.yml 中 collections: 这一行最后一次修改的 commit 信息

第 1、3 小题在 lecture 中演示过，而第 2 小题据提示比较简单。

0. 用 git clone <URL> <folder>*（必备基础技能）*克隆课程仓库：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise$ git clone https://github.com/missing-semester/missing-semester missing-semester
   Cloning into 'missing-semester'...
   remote: Enumerating objects: 2344, done.
   remote: Counting objects: 100% (1487/1487), done.
   remote: Compressing objects: 100% (543/543), done.
   remote: Total 2344 (delta 980), reused 964 (delta 941), pack-reused 857
   Receiving objects: 100% (2344/2344), 15.61 MiB | 1.28 MiB/s, done.
   Resolving deltas: 100% (1392/1392), done.
   

1. 不妨运用 Topic 5 所讲解的 别名 (alias) 知识，简化 git log 的相关图示法命令：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/test/demo$ alias gl='git log --all --graph --decorate'
   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/test/demo$ alias gl1='gl --oneline'
   

   **提示：**可以在配置文件 ~/.bashrc 中设定默认的 alias。

   • gl：包含详细 commit 的信息

     cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$ gl > gl_res.log
     cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$ vim gl_res.log
     

     结果极长，共 4218 行。

   • gl1：缩略信息，每个 commit 仅一行

     *   d38f585 (HEAD -> master, origin/master, origin/HEAD) Merge branch 'alexandr-gnrk/update-jupyter-binding'
     |\
     | * f600f32 Update Vim binding for Jupyter
     |/
     * 2253e4e Switch recommended app to Rectangle
     * 18ee93c Ignore Reddit URLs when checking links
     *   2ab1b78 Merge branch 'alkock/master'
     |\
     | * 98d90f8 added german translation
     |/
     * bd75a78 Fix broken links
     *   7330a25 Merge branch 'fipachu/git-aliases'
     |\
     | * 6fc734b Add more useful overview of Git aliases
     |/
     *   f45234f Merge branch 'Nikitaz1410/patch-2'
     ...
     

     部分较新的历史如上，共 885 行。

   **提示：**当 git log 等其它 git 命令的信息较长时会显示前一部分信息并自动进入某种 “交互” 模式，上下移动方法同 Vim，H 键显示帮助，Q 键退出。

2. 考虑使用 Topic 2 提及的 tldr 工具查询所需用法：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$ tldr git log
   	...
     Show a history of commits.
     More information: https://git-scm.com/docs/git-log.
   	...
     - Show the history of a particular file or directory, including differences:
       git log -p path/to/file_or_directory
   	...
   

   由此得知 git log -p + 文件/文件夹

   后来发现不应该如上加上 -p flag，其会显示所有 “differences”，直接加文件即可：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$ git log README.md
   commit 9ef9db72211fefc00caaa7133b35dda4a99acccf
   Author: Anish Athalye <me@anishathalye.com>
   Date:   Thu Oct 27 20:28:41 2022 -0400
   
       Add Docker setup for easier development
   ...
   

   因此显然是授课老师 Anish Athalye 最后修改了 README.md。

3. lecture 中演示了。先 git blame + 文件并找到目标信息对应的 commit，随后 git show <commit> 得到其相关信息：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$ git blame _config.yml
   ...
   a88b4eac (Anish Athalye 2020-01-17 15:26:30 -0500 18) collections:
   a88b4eac (Anish Athalye 2020-01-17 15:26:30 -0500 19)   '2019':
   ...
   

   $\Rightarrow$ commit 哈希值为 a88b4eac

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$ git show a88b
   commit a88b4eac326483e29bdac5ee0a39b180948ae7fc
   Author: Anish Athalye <me@anishathalye.com>
   Date:   Fri Jan 17 15:26:30 2020 -0500
   
       Redo lectures as a collection
   ...
   

   所以对应 commit 的信息为 “Redo lectures as a collection”

练习三

为应对误将不应被 Git 管理的内容，如某大文件或敏感信息，commit 的情况，学习 Github 上的相关文章，随后模拟上述情形下删除目标文件。

学习文章知，可以使用两种工具（均需安装）：

• git filter-repo
• BFG Repo-Cleaner

练习四

修改某仓库中的文件，随后依次 git stash、git log --all --oneline、git stash pop 巩固 git stash 的技能，并思考其可能适用于在何种情况。

​ stash vt. 藏匿; 隐藏; 存放; 贮藏（百度翻译)

lecture 中也演示过 git stash，其可 “隐藏” 所做的修改，并以 git stash pop 恢复。

1. 修改 README.md 之后 git stash：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/test_git_stash$ echo '**REMOVED**' > README.md
   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/test_git_stash$ git status
   On branch master
   Your branch is up to date with 'origin/master'.
   
   Changes not staged for commit:
     (use "git add <file>..." to update what will be committed)
     (use "git restore <file>..." to discard changes in working directory)
           modified:   README.md
   
   no changes added to commit (use "git add" and/or "git commit -a")
   

2. git log：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/test_git_stash$ git log --all --oneline
   7fca419 (refs/stash) WIP on master: d38f585 Merge branch 'alexandr-gnrk/update-jupyter-binding'
   088c991 index on master: d38f585 Merge branch 'alexandr-gnrk/update-jupyter-binding'
   d38f585 (HEAD -> master, origin/master, origin/HEAD) Merge branch 'alexandr-gnrk/update-jupyter-binding'`
   ...
   

   可以发现在 HEAD commit 之上多了两条 commit！且最后一条为 refs/stash。

3. 用 git stash pop 恢复：

   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/test_git_stash$ git stash pop
   On branch master
   Your branch is up to date with 'origin/master'.
   
   Changes not staged for commit:
     (use "git add <file>..." to update what will be committed)
     (use "git restore <file>..." to discard changes in working directory)
           modified:   README.md
   
   no changes added to commit (use "git add" and/or "git commit -a")
   Dropped refs/stash@{0} (7fca419c92d8bff936036a4ca32b277d11c1849a)
   cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/test_git_stash$ git log --all --oneline | head -10
   d38f585 Merge branch 'alexandr-gnrk/update-jupyter-binding'
   ...
   

   直接跳出了 README.md 被更新的提示，且此时 git log 已无之前新增的 commit 记录。

git stash 应该在修改文件后又想看其之前的内容时非常有用。若无 git stash，恐怕只能先将文件存在别处，随后 git checkout -- <file> 丢弃修改。

练习五

在 Git 的配置文件 ~/.gitconfig 中创建 alias，以便使用 git graph 便能得到 git log --all --graph --decorate --oneline 的结果。

在 .gitconfig 文件中加入：

[alias]
        graph = log --all --graph --decorate --oneline

测试如下：

cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$ diff <(git graph) <(git log --all --graph --decorate --oneline)
cowbby@LAPTOP-UD6KDALFP:~/Missing Semester/6_Version Control(git)/exercise/missing-semester$

可见两者输出完全一样。

练习六

You can define global ignore patterns in ~/.gitignore_global after running git config --global core.excludesfile ~/.gitignore_global. Do this, and set up your global gitignore file to ignore OS-specific or editor-specific temporary files, like .DS_Store.

练习七

Fork the repository for the class website, find a typo or some other improvement you can make, and submit a pull request on GitHub (you may want to look at this). Please only submit PRs that are useful (don’t spam us, please!). If you can’t find an improvement to make, you can skip this exercise.
u may want to look at this). Please only submit PRs that are useful (don’t spam us, please!). If you can’t find an improvement to make, you can skip this exercise.