How to recover dropped data from stash

How to recover from a git mistake

Don't let an error in a git command wipe out days of work.

How to recover from a git mistake
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Today my colleague almost lost everything that he did over four days of work. Because of an incorrect git command, he dropped the changes he'd saved on stash. After this sad episode, we looked for a way to try to recover his work... and we did it!

First a warning: When you are implementing a big feature, split it in small pieces and commit it regularly. It's not a good idea to work for a long time without committing your changes.

Now that we've gotten that out of the way, let's demonstrate how to recover changes accidentally dropped from stash.

My example repository, which has only one source file, main.c, looks like this:

missing_data_from_stash_01.jpeg

Repository with one source file

José Guilherme Vanz, CC BY

It has only one commit, the initial commit:

missing_data_from_stash_02.jpeg

One commit

José Guilherme Vanz, CC BY

The first version of our file is:

missing_data_from_stash_03.jpeg

First version of the file

José Guilherme Vanz, CC BY

I'll start to code something. For this example, I do not need to make a big change, just something to put in the stash, so I will just add a new line. The git-diff output should be:

missing_data_from_stash_04.jpeg

git-diff output

José Guilherme Vanz, CC BY

Now, suppose that I want to pull some new changes from a remote repository, but I'm not ready to commit my change. Instead, I decide to stash it, pull the remote repository's changes, then apply my change back to the master. I execute the following command to move my change to stash:

git stash

Looking into the stash with git stash list, I can see my change there:

missing_data_from_stash_06.jpeg

Output of changes in our stash

José Guilherme Vanz, CC BY

My code is in a safe place and the master branch is clean (I can check this with git status). Now I just need to pull the remote repository changes, then apply my change on the master, and I should be set.

But I accidentally execute:

git stash drop

which deletes the stash, instead of:

git stash pop

which would have applied the stash before dropping it from my stack. If I execute git stash list again, I can see I dropped my change from the stash without applying it on the master branch. OMG! Who can help me?

Good news: git did not delete the object that contains my change; it just removed the reference to it. To prove this, I use the git-fsck command, which verifies the connectivity and validity of the objects in the database. Here's the output after I executed the git-fsck command on the repository:

missing_data_from_stash_07.jpeg

Output after executing the git-fsck command on the repository

José Guilherme Vanz, CC BY

With the --unreachable argument, I asked git-fsck to show me the objects that are unreachable. As you can see, it showed no unreachable objects. After I dropped the changes on my stash, I executed the same command, and received a different output:

missing_data_from_stash_08.jpeg

Output after dropping changes on stash

José Guilherme Vanz, CC BY

Now there are three unreachable objects. But which one is my change? Actually, I don't know. I have to search for it by executing the git-show command to see each object.

missing_data_from_stash_09.jpeg

Output after executing the git-show command

José Guilherme Vanz, CC BY

There it is! The ID 95ccbd927ad4cd413ee2a28014c81454f4ede82c corresponds to my change. Now that I found the missing change, I can recover it! One solution is check out the ID into a new branch or apply the commit directly. If you have the ID of the object with your changes, you can decide the best way to put changes on the master branch again. For this example, I will use git-stash to apply the commit on my master branch again.

git stash apply 95ccbd927ad4cd413ee2a28014c81454f4ede82c

Another important thing to remember is git runs its garbage collector periodically. After a gc execution, you can no longer see the unreachable objects using git-fsck.

This article was originally published on the author's blog and is reprinted with permission. 

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About the author

Jose Guilherme Vanz - I'm José Guilherme Vanz, from south Brazil. Working as Software Engineer. I love Open Source and programming