Git: How do you replace your current working directory with a previous commit without branching or git revert?

Question

Is there an easy way to the following with git?

Basically I want to create a new commit at the top of my commit history that is equivalent to a previous com

Answer 1

To create a new commit, restoring the content of an old commit, you can:

• First, mark the current HEAD of your branch (assuming master here): we will need to move that HEAD without modifying master, so let's create a new temporary branch called 'tmp' where master is.

  git checkout master
  git checkout -b tmp
  

(yes, that is against the "without branching" of the question, but you will delete that tmp branch soon)

• Then we go back to an older commit with the right content.

  git reset --hard <old_commit>
  

That resets the index (and working tree) to the right content, but that also moves HEAD. However, that moves tmp HEAD, not master HEAD.

• move back tmp HEAD to where master is, but without modifying the index or the working tree (which are representing what we need for a new commit)

  git reset --soft master
  

• make a new commit, on top of master/tmp HEAD, which represents the right content (the old commit).

  git commit -m "new commit, image of an old one"
  

• Finally, force master to be where tmp is: one new commit later.

  git branch -M tmp master
  git checkout master
  git branch -d tmp
  

Now a regular git push is enough, any collaborator can simply pull as usual, and still get the old reset content.

git push

Answer 2

In situation when you want to return to some state you do following:

git reset --hard 49a732c

This step put your master branch into desired state. If you want to save you previous branch state:

git checkout 48ah14s -b archive/my-unrecognized-experiments

You still can do it after reset because reset doesn't delete commits.

PS Branching is essential part of git. It is better to teach branching then teach such complicated (in git) things as you pictured.

EDIT If you want your master to stay consistent with remotes:

git reset 49a732c # move HEAD back, all changes still in working tree
git commit -am "My unrecognized experiments" # save all changes as one commit
git reset --hard 48ah14s  # restore master HEAD
git revert <hash of my unrecognized experiments> # apply reverted changes to master

Answer 3

Assuming you start from a clean worktree, you could do:

cd <root_directory_of_your_repo>
git checkout master
git checkout 49a732c -- .

When you specify a file (in this case . (the root directory of your repo)) as an argument to git checkout, the checkout will not switch branch (the repo HEAD will remain the same). It will just update the index to make that file match the version of that file from the specified commit. Since you specified the root directory of the repo, all files in the index will be updated to match the specified commit 49a732c