Undoing and recovering

One of the main points of version control is that you can go back in time to recover. Let's have look at safe commands that do not modify the commit history.

Undoing uncommitted changes#

Unstaged file#

Let's edit config.yml and remove the line sample_ids: ["SRR935090","SRR935091","SRR935092"]. Run git status, it will tell you that there are modifications in one file (config.yml) compared to the previous commit.

For unstaged file it is possible to have details about the modifications made.

git diff config.yml

You now realize that this modification was wrong. Use git restore to remove all modifications made since last commit.

git restore config.yml
git status

As you can see, Git tells us that this file has not been modified since last commit.

Staged file#

Let's edit config.yml, remove the line sample_ids: ["SRR935090","SRR935091","SRR935092"], stage the file and run git status.

Stage and commit the first file

git add config.yml
git status

Git tells us that there is a staged file. You now realize that this modification was wrong. You have to first unstage the file before to clean the modifications:

git restore --stage config.yml
git status
git restore config.yml
git status

Tip

In case you want to throws away everything that is not in last commit (HEAD) you can use git reset --hard HEAD. It is apply on all files, staged and unstaged.

Undoing committed changes#

Let's edit config.yml, remove the line sample_ids: ["SRR935090","SRR935091","SRR935092"], stage the file, commit, and run git status.
```
git add config.yml
git commit -m "remove sample_ids line"
git status
```

The git status is not really helpfull here as we already commited our modifications

git log

The git log command show us the message we entered in previous commits.

To see modification made in the previous commit you can use:

git diff HEAD^

Tip

Too see the modifications between the last commit and a particular commit you can use git diff <commit_id>. It is also possible to compare the differences between two commits: git diff <commit_id1> <commit_id2>.

You now realize that the latest commit was a mistake and you wish to undo it:

git log --online
git revert <commit>

This creates a new commit that does the opposite of the reverted commit. The old commit remains in the history.

Note

You can revert any commit, no matter how old it is. It doesn’t affect other commits you have done since then - but if they touch the same code, you may get a conflict (which we’ll learn about later).

Quick recap

We added four important Git commands to our repertoire:

git diff <file> list all modifications made on a file since last commit
git restore <file> cancels the modifications of an unstaged file
git restore --staged <file> unstage a staged file
git revert <commit> does the opposite of the reverted commit