Revert & reset¶

Revert¶

git revert is the friendly way of undoing a commit and, frankly, the only acceptable way to do it, if you are working in remote repositories with a lot of contributors.

git revert adds a new commit that will undo the changes of the commit you want revoked. For example, if an unwanted commit adds the text "Oops, my cat is walking over my keywalrhlgk" to the bottom of a specific file, a revert on that commit will remove "Oops, my cat is walking over my keywalrhlgk" from the bottom of that file. It will effectively restore it to the state before that commit had been made.

The great thing is that both your mistake, and the correction of said mistake, are preserved in your history. Thus, making it fully non-destructive.

Example: git revert¶

We have accidentally committed a change in the development branch with commit hash damn. We want to use git revert to undo this change.

# Ensure we are checked out in the right branch
git switch development

# Revert the unwanted commit
git revert damn

gitGraph
  commit id: "A"
  commit id: "B"
  branch development
  checkout main
  commit id: "C"
  commit id: "D"
  checkout development
  commit id: "I"
  commit type: REVERSE id: "damn"
  commit id: "II"
  commit type: HIGHLIGHT id: "undo_damn"

The commit with hash undo_damn has now removed the changes made by commit damn.

Reset¶

git reset will move a branch to a commit back in time, in the sense that it appears as if the commit had never been made in the first place.

# Checkout the branch that has the commit we want to reset
git switch development

# Reset the branch, discarding the current commit
git reset HEAD

# Reset the branch, discarding the last three commits
git reset HEAD~3

git reset is also a way to clear changes that have been staged pending a commit, using git add. Consider the following example:

# Let's stage two arbitrary files
git add script.py
git add README.md

# If we would want to unstage README.md
git reset README.md

# Or if we would want to unstage all files
git reset

However, the command can also be modified using the --hard flag. This way, the command can be used to hard delete commits. Commits reset this way will be entirely removed from the commit history - and file history - and cannot be retrieved. It is therefore fully destructive.

Example: git reset --hard¶

We have accidentally committed a change in the development branch with commit hash damn. We want to use git reset --hard to completely obliterate this mistake from the annals of history.

gitGraph
  commit id: "A"
  commit id: "B"
  branch development
  checkout main
  commit id: "C"
  checkout development
  commit id: "I"
  commit type: REVERSE id: "damn"
  checkout main
  commit id: "D"

# Ensure we are checked out in the proper branch
git switch development

# Hard reset the branch one commit back from the current checked-out state
git reset --hard HEAD~

This will result in the following commit history:

gitGraph
  commit id: "A"
  commit id: "B"
  branch development
  checkout main
  commit id: "C"
  checkout development
  commit id: "I"
  checkout main
  commit id: "D"