Do not believe a thing because you read it in a book! Do not believe a thing because another has said it so! Find out the truth for yourself.

Bill Vaughan, according to the Internet

Don't believe all I say, RTFM.

Move your HEAD with Git

revert, checkout, reset

git revert

git revert

• Cancels a commit by creating an opposite commit
• Useful to "remove" commits already publicly published
• Cancel live breaking merge

git revert

Format: git revert <git-object>

example: git revert 123abc

git revert

Revert merges

git revert

• Special cases, merges have multiple parents
• Which part of the merge to revert
• In previous example: myBranch1, myBranch2 or both can be reverted
• -m # option specify the parent to revert

Revert merges

git checkout

git checkout

• Different behaviour depending on arguments
• git object and path can be provided or just git object

git checkout [gitObject] path

• Change state of given file 

git checkout [gitObject] path

• Does NOT change HEAD
• If no object given, discards any unstaged changes
• If an object is given, changes the file to match the object. Stages the diff between the object and HEAD

git checkout gitObject

• Change the position of HEAD and the state of the working tree
• Links HEAD to targeted object
• If object is NOT a branch, HEAD is detached
• Used to switch between versions of the code
• Does NOT change the state of branches

"cd" for git

git checkout gitObject

git checkout gitObject

git reset

git reset

• Different behaviour depending on arguments
• git object and path can be provided or just git object

git reset [gitObject] path

• Set the staged state of given file at the state of the given object
• Sets the modified state of the file to keep the file unchanged
• Corollary: If no object is provided (HEAD used by default), the command unstages the file

git reset gitObject

• Moves HEAD to the provided object
• If HEAD was on a branch, moves the branch tip as well
• makes the commits from the branch's old position potentially unaccessible (unless using reflog, that is)
• Useful to "get rid of" the n last commits of a branch

git reset gitObject

git reset gitObject

git reset gitObject

git reset gitObject

What about changes in between?

• git reset --soft : keep difference staged
• git reset --mixed : keep differences in working tree (default)
• git reset --hard : discard differences

Conclusion

Know what you want to do to know what to do

Conclusion

If you want to:

• Cancel a published commit

git revert gitObject

Conclusion

If you want to:

• Go somewhere in your commit history
• Go to a specific branch

git checkout gitObject

Conclusion

If you want to:

• Create a new branch and switch on it

git branch theBranch

git checkout theBranch

or

git checkout -b theBranch

Conclusion

If you want to:

• remove local modifications in a file
• change a file to a desired point in the history

git checkout [gitObject] path

Conclusion

If you want to:

• move the tip of a branch to somewhere else (eg remove the last commits or take the remote version of a branch)

git reset --hard newPosition

Conclusion

If you want to:

• lose all local changes (staged or not)
• cancel an ongoing merge

git reset --hard

Conclusion

If you want to:

• unstage your changes

git reset