Git/Github Usage and Instruction

note:

make sure that target local files are located in repository folder.
Cannot operate files outside repository folder.
two file transferring paths: http and SSH( Recommaded, openssh required)
*set authentication(鉴权).
- In .git/config, add username and passwd after url

config git

totally new env
create ssh key

ssh-keygen -t rsa -C "your_email@youremail.com"

set user info

git config --global user.name "your name"  
git config --global user.email "your_email@youremail.com"

check user

git config user.name  
git config user.email

check all information
```
git config -l
```

repository initializatioin

相关操作，在 GitHub 创建新 repository 时，会出现提醒，内容如下：

create a new repository on the command line

echo "# README" >> README.md
git init
git add README.md
git commit -m "first commit"
git branch -M main
git remote add origin <git url>
git push -u origin main

push an existing repository from the command line

git remote add origin <git url>
git branch -M main
git push -u origin main

repository operation

local repository trilayer structure

add files to index(cache space)
```
git add file1 file2 ...  
```
add version annatation
```
git commit -m "modification_annotation"
```
view current git status
```
git status
```
push modification to remote repository
```
git push origin master
```
pull latest version from repostory
```
git pull
```

about version

get version list (not incluede the versions hereafter)
```
git log [ --pretty=online ]
```
set current version
```
git reset --hard version_number
```
get all versions
```
git reflog
```

branch command

branch pattern

list branch
```
git branch
```
create branch
```
git branch name
```
switch branch
```
git checkout name
```
creat and switch branch
```
git checkout -b name
```
delete
```
git branch -d name
```
merge
```
git merge names
```

Note: the operations in different branches do not influence each other. Merge operation is in need af final.

solve conflicts

add git sshkey into Github

create a SSH key
```
ssh-keygen -t rsa -C "your_email@example.com"
```
default generated file ~/.ssh/id_rsa.pub
add SSH key content into github SSH
setting -> SSH and GPG keys

日常遇到的问题

Offending RSA key in ~/.ssh/known_hosts:2

在进行 git push/pull 的时候，发生如下错误：

$ ssh -T git@github.com
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
SHA256:uNVztksCshcc0ueBujQXVUpZIDTMczCvjtD2.
Please contact your system administrator.
Add correct host key in ~/.ssh/known_hosts to get rid of this message.
Offending RSA key in ~/.ssh/known_hosts:2
RSA host key for github.com has changed and you have requested strict checking.
Host key verification failed.