git 快速入门及常见用法
身为技术人员，都知道Git是干嘛的。从服务端角度它是代码仓库，可以多人协作、版本控制、高效处理大型或小型项目所有内容；从客户端讲，它能够方便管理本地分支、且与服务端代码的同步，从拉取、合并、提交等等管理分支都靠它！
Git轻量、易于学习，如果不用搭建和维护代码仓库的话（运维职责），只要掌握几个git常用命令即可在工作中轻松应对。
下面简单介绍几个概念，同时列出工作中常用命令：
主要概念
快速入门，弄明白以下几个概念即可：
- 工作区（Working Directory）：就是你在电脑里能看到的目录，或克隆（clone）下来的目录；
- 版本库（Repository）：工作区里面有一个隐藏目录.git，这个不是工作区，而是Git的版本库；
- 暂存区（stage）：版本库中有一个叫stage的暂存区，git add可以把要提交的内容放到暂存区；
- 主分支（master）：版本库还有一个叫master的主分支，git commit把暂存区所有内容提交到当前分支；
主要用法
工作中，一般我们提交代码只要四步：
- 第一步，git pull 拉取代码，提交代码前确保和服务端仓库一致，避免冲突；
- 第二步，git add ./your_file.txt 把文件添加进去，实际就是从工作区提交到暂存区；
- 第三步，git commit -m 'first commit'提交更改，再把暂存区所有内容提交到当前分支（默认master）；
- 第四步，git push [remoteName]推送到远程仓库，也就是推到服务端，这样别人就能拉取pull你的代码；
常见用法
平时工作也就用到上面四个步骤，当然了凡事有例外，下面说几个例外的处理办法：
一、checkout切换分支
git checkout
git checkout -b
参考链接：https://git-scm.com/docs/git-checkout
二、git提交后撤销问题
撤销得分三种情况：
- 第一，已经修改文件但未执行git add的撤销方法；
我故意在.gitignore文件修改之后且没有git add，直接通过git checkout --撤销；
但是此命令不会撤销新建的文件，因为新建文件还没加入到Git管理系统中，所以git是未知的，自己手动删除就好了。
λ git status
On branch masterYour branch is up-to-date with 'origin/master'.
nothing to commit, working tree clean
D:\learning\git\work (master -> origin)
λ git statusOn branch masterYour branch is up-to-date with 'origin/master'.
Changes not staged for commit:
(use "git add ..." to update what will be committed)
(use "git checkout -- ..." to discard changes in working directory)
modified: .gitignoreno changes added to commit (use "git add" and/or "git commit -a")
D:\learning\git\work (master -> origin)
λ git checkout -- .gitignore
D:\learning\git\work (master -> origin)
λ git status
On branch master
Your branch is up-to-date with 'origin/master'.
nothing to commit, working tree clean
扩展：
命令git checkout -- .gitignore意思就是，把.gitignore文件在工作区的修改全部撤销，这里有两种情况：
一种是.gitignore自修改后还没有被放到暂存区，现在撤销修改就回到和版本库一模一样的状态；
一种是.gitignore已经添加到暂存区，又作了修改，现在，撤销修改就回到添加到暂存区后的状态。
总之，就是让这个文件回到最近一次git commit或git add时的状态。
参考链接：https://www.liaoxuefeng.com/wiki/896043488029600/897889638509536
- 第二，已经修改文件且git add的撤销方法
需要先执行git reset .gitignore撤销到未git add状态，再执行第一步即可。
λ git add .gitignore
D:\learning\git\work (master -> origin)λ git statusOn branch masterYour branch is up-to-date with 'origin/master'.
Changes to be committed: (use "git reset HEAD ..." to unstage)
modified: .gitignoreD:\learning\git\work (master -> origin)λ git reset .gitignoreUnstaged changes after reset:M .gitignoreD:\learning\git\work (master -> origin)λ git statusOn branch masterYour branch is up-to-date with 'origin/master'.
Changes not staged for commit:
(use "git add ..." to update what will be committed)
(use "git checkout -- ..." to discard changes in working directory)
modified: .gitignoreno changes added to commit (use "git add" and/or "git commit -a")
D:\learning\git\work (master -> origin)λ git checkout -- .gitignoreD:\learning\git\work (master -> origin)λ git statusOn branch masterYour branch is up-to-date with 'origin/master'.
nothing to commit, working tree clean - 第三，Git已经commit如何撤销：
通过git reset --hard commitid直接回到未修改状态。
λ git add .gitignore
λ git commit -m "test"
#(省略无用部分)λ git statusOn branch masterYour branch is ahead of 'origin/master' by 1 commit.
(use "git push" to publish your local commits)
nothing to commit, working tree cleanD:\learning\git\work (master -> origin)λ git logcommit b7de9378f39834dbc8304d4a8d30f39a4003c673 (HEAD -> master)Author: test
Date: Mon Sep 14 02:59:02 2020 +0800
testcommit b3ed1078e543cdb26b984dac584df9db7553d506 (origin/master, origin/HEAD)Author: test
Date: Mon Sep 14 02:39:54 2020 +0800
09142020
D:\learning\git\work (master -> origin)λ git reset --hard b3ed1078e543cdb26b984dac584df9db7553d506HEAD is now at b3ed107 09142020
D:\learning\git\work (master -> origin)λ git logcommit b3ed1078e543cdb26b984dac584df9db7553d506 (HEAD -> master, origin/master, origin/HEAD)Author: test
Date: Mon Sep 14 02:39:54 2020 +0800
09142020
D:\learning\git\work (master -> origin)λ git statusOn branch masterYour branch is up-to-date with 'origin/master'.
nothing to commit, working tree clean 三、git stash保存和恢复工作区内容
git stash可以将你已经修改，但不想提交（git push）的代码临时保存到堆栈中，也就是回归到你git pull时的状态。然后就能随意切换分支救火，完成后切换回来再git push pop即可恢复之前的修改内容。stash不仅可以恢复到原先开发的分支，也可以恢复到其他任意指定的分支上（可跨分支）。
- git stash
保存当前工作进度，会把暂存区和工作区的改动保存起来。执行完之后再git status，会发现当前是一个干净的工作区，没有任何改动。
使用git stash save 'message...'可以添加一些注释
- git stash list
显示保存进度的列表。也就意味着，git stash命令可以多次执行。 - git stash pop
恢复最新的进度到工作区。git默认会把工作区和暂存区的改动都恢复到工作区。 - git stash pop stash@{stash_id}
恢复指定的进度到工作区。stash_id通过git stash list命令得到的通过git stash pop命令恢复进度后，会删除当前进度。 - git stash drop stash@{stash_id}
可以使用git stash drop命令，后面可以跟stash_id或使用git stash clear命令，删除所有缓存的stash - git stash show
查看堆栈中最新保存的stash和当前目录的差异
举个例子
- 修改.gitignore文件，新建test.txt文件。在执行stash发现新增文件不会被存储；
- git add之后在stash发现工作区是干净的；
- 说明没有在git版本控制（git add）中的文件，不能被git stash 保存；
- 最后通过git stash pop恢复。
λ git status
On branch masterYour branch is up to date with 'origin/master'.
Changes not staged for commit:
(use "git add ..." to update what will be committed)
(use "git restore ..." to discard changes in working directory)
modified: .gitignoreUntracked files: (use "git add ..." to include in what will be committed)
test.txtno changes added to commit (use "git add" and/or "git commit -a")
D:\learning\git\timed_tasks (master -> origin)
λ git stashSaved working directory and index state WIP on master: 542a055 create .gitignore
D:\learning\git\timed_tasks (master -> origin)
λ git statusOn branch masterYour branch is up to date with 'origin/master'.
Untracked files: (use "git add ..." to include in what will be committed)
test.txtnothing added to commit but untracked files present (use "git add" to track)
D:\learning\git\timed_tasks (master -> origin)
λ git add test.txt
D:\learning\git\timed_tasks (master -> origin)
λ git stashSaved working directory and index state WIP on master: 542a055 create .gitignore
D:\learning\git\timed_tasks (master -> origin)
λ git stash liststash@{0}: WIP on master: 542a055 create .gitignore
stash@{1}: WIP on master: 542a055 create .gitignore
stash@{2}: WIP on (no branch): 542a055 create .gitignore
D:\learning\git\timed_tasks (master -> origin)
λ git statusOn branch masterYour branch is up to date with 'origin/master'.
nothing to commit, working tree clean
D:\learning\git\timed_tasks (master -> origin)
λ git stash show test.txt | 0
1 file changed, 0 insertions(+), 0 deletions(-)
D:\learning\git\timed_tasks (master -> origin)
λ git stash popOn branch masterYour branch is up to date with 'origin/master'.
Changes to be committed:
(use "git restore --staged ..." to unstage)
new file: test.txt
Dropped refs/stash@{0} (b69da2894d5e7f511be18277c5a0cd4582fbf453)
D:\learning\git\timed_tasks (master -> origin)
λ git statusOn branch masterYour branch is up to date with 'origin/master'.
Changes to be committed:
(use "git restore --staged ..." to unstage)
new file: test.txt
Tip：如果你修改的所有文件都不想要了怎么办？可通过git stash清空，懂吧？
λ git status
On branch masterYour branch is up to date with 'origin/master'.
Changes to be committed:
(use "git restore --staged ..." to unstage)
new file: test.txt
D:\learning\git\timed_tasks (master -> origin)
λ git stashSaved working directory and index state WIP on master: 542a055 create .gitignore
D:\learning\git\timed_tasks (master -> origin)
λ git stash clearD:\learning\git\timed_tasks (master -> origin)
λ git statusOn branch masterYour branch is up to date with 'origin/master'.
nothing to commit, working tree clean
λ git status
On branch masterYour branch is up to date with 'origin/master'.
Changes to be committed:
(use "git restore --staged ..." to unstage)
new file: test.txt
D:\learning\git\timed_tasks (master -> origin)
λ git stashSaved working directory and index state WIP on master: 542a055 create .gitignore
D:\learning\git\timed_tasks (master -> origin)
λ git stash clearD:\learning\git\timed_tasks (master -> origin)
λ git statusOn branch masterYour branch is up to date with 'origin/master'.
nothing to commit, working tree clean