Undo and rollback in git

1 , undo before commit


Undo not added to the staging area (before add)
git status
git checkout .


Undo added to the staging area (after add)

git reset HEAD : roll back the files that have been added to the staging area to the state that was not added to the staging area, and then git checkout to return to the most original state



2 , Cancellation after commit

(
git add .

git commit -m "commit"

git  push  origin brandname
)
Undo after a series of operations


I do not want this operation to take effect


git revert commitId (commit id)


git push origin brandname

This operation will undo the last push



On this branch, a revert commit record will be generated


revert is negative and positive, what does it mean, that is, when reverting for the first time, the last push command will be invalid, and after reverting again, it will go back to the previous state.
Introduce in detail

For example, I operate a file UserController.java
 
 Change userName to username after a series of git operations
 git add .
 git commit -m "commit"
 git push orgin
 After that, do git revert commitId again
 Then do git push origin branchname
 userName or userName,


If I revert again,
git revert
git push origin branchname
Change userName to username.

Summarized as:

git revert takes effect when it is odd, and fails when it is even

3 , git rollback:
Roll back git to a commit operation, and all operations before the commitId will be invalid (this method is not recommended and has risks),

git reset --hard commitId


git push origin branchname --force (force overwrite) 

is not recommended because it is irreversible