# Git / Github 常用進階指令

## `git pull` v.s. `git fetch`

### 本機上 git 的 branch 與 GitHub 上的 Remote Branch


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#### `git pull` v.s. `git fetch`
> #### 都是把 code 從 GitHub 上拿下來的方式
> #### Retrieve changes from a remote repository

#### 情況舉例

### 比較


### `git fetch`
Fetching allows us to download changes from a remote repository, BUT those **changes will NOT be automatically integrated into our working files.**

:arrow_right: It lets you see what others have been working on, WITHOUT having to merge those changes into your local repo.

:thought_balloon: "please go and get the latest information from Github, but don't screw up my working directory."

#### 圖解

I now have those changes on my machine, but if I want to see them I have to checkout origin/master. My master branch is untouched!

#### syntax
<img src="https://i.imgur.com/uzKeMma.png" width="270px">

<img src="https://i.imgur.com/mMP1Hzw.png" width="330px">

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### `git pull`

#### :thought_balloon: "go and download data from Github AND immediately update my local repo with those changes"

### 圖解

:exclamation: **pulls can result in merge conflicts!!**

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## `git reset`
> #### Undo & Time-Traveling

### `git reset <commit-hash>`

#### 情境：git commit 以後，才發現想要那個 commit 在另一個 branch

<img src="https://i.imgur.com/PV71SNH.png">

:arrow_up: 已經 commit 了，卻發現不是要 commit 在這個 branch 上

<img src="https://i.imgur.com/Mp8LMDe.png">

:arrow_up: 用 **`git reset <commit-hash>`** 可以 undo 這個 commit 的紀錄，但到這個 commit 的時間點所做的內容仍然還在（然後就可以重新 commit 在另一個 branch ）

### `git reset --hard <commit-hash>`

:arrow_up: 用 **`git reset --hard <commit-hash>`** ，會 undo 這個 commit，並且 time travle 到這個 commit 時間點之前的內容

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### `git reset HEAD~<commitBackwardNum>`
#### 情境：想要回頭看前面的 commit 的狀態


:arrow_up: 用 **`git reset HEAD~<commitBackwardNum>`** ，可以讓我們 time travel 回到前 n 個 commit

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## `git rebase`
(下次再補細節，先大致介紹)

> ### 1. As an alternative to merging
> ### 2. As a cleanup tool

### As an alternative to merging
#### issue with `git merge` during collaboration
<img src="https://i.imgur.com/UFa4yz2.png" width="400px">

:arrow_up: 同時有很多branch，想要 update 到最新的版本的話，我們的 commit 紀錄會有很多是 merge


<img src="https://i.imgur.com/QK0XSqS.png" width="300px">

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### As a cleanup tool
> #### REWRITE, DELETE, RENAME, or even REORDER commits

#### Interactive Rebase
搭配使用：`pick`, `reword`, `edit`, `fixup`, `drop`