Checkout commit

To view complete snapshot of the project at a point in time, checkout the commit
Restore the working directory to the snapshot stored in that commit

git checkout commit

When you checkout, the repo is in detached head state
Each commit points to the previous commit, using this git maintains history
You can have multiple branches in git
Every git has a default branch called master (trunk)
Way git represents a branch is using a pointer
master is pointing to the last commit
As we create new commit master moves forward to point to the last commit
Because we can have multiple branches. git need to know what is the branch we are currently working on git uses another pointer called head.
head points to the current branch we are working on
As we create new commit head and master pointer moves forward to point to the last commit
When we checkout a particular commit, head pointer moves to that commit. this is called detached head. head is not attached to branch anymore
We shouldn't create new commits only view our code
if you create new commit, it will not be reachable by any other commit and it will become dead commit
git checks periodically for dead commit, removes it to save space

git log --oneline
git log --oneline --all
git checkout master

Git