How can I recover a lost commit in Git?

First, got "your branch is ahead of origin/master by 3 commits" then my app has reverted to an earlier time with earlier changes.

How can I get what I spent the last 11 hours doing back?

git reflog is your friend. Find the commit that you want to be on in that list and you can reset to it (for example:git reset --hard e870e41).

(If you didn't commit your changes... you might be in trouble - commit early, and commit often!)

Before answering, let's add some background, explaining what this HEAD is.

First of all what is HEAD?

HEAD is simply a reference to the current commit (latest) on the current branch.
There can only be a single HEAD at any given time (excluding git worktree).

The content of HEAD is stored inside .git/HEAD and it contains the 40 bytes SHA-1 of the current commit.

---

detached HEAD

If you are not on the latest commit - meaning that HEAD is pointing to a prior commit in history it's called detached HEAD.

On the command line, it will look like this - SHA-1 instead of the branch name since the HEAD is not pointing to the tip of the current branch:

---

A few options on how to recover from a detached HEAD:

---

git checkout

git checkout <commit_id>
git checkout -b <new branch> <commit_id>
git checkout HEAD~X // x is the number of commits t go back

This will checkout new branch pointing to the desired commit.
This command will checkout to a given commit.
At this point, you can create a branch and start to work from this point on.

# Checkout a given commit.
# Doing so will result in a `detached HEAD` which mean that the `HEAD`
# is not pointing to the latest so you will need to checkout branch
# in order to be able to update the code.
git checkout <commit-id>

# Create a new branch forked to the given commit
git checkout -b <branch name>

---

git reflog

You can always use the reflog as well.
git reflog will display any change which updated the HEAD and checking out the desired reflog entry will set the HEAD back to this commit.

Every time the HEAD is modified there will be a new entry in the reflog

git reflog
git checkout HEAD@{...}

This will get you back to your desired commit

---

git reset --hard <commit_id>

"Move" your HEAD back to the desired commit.

# This will destroy any local modifications.
# Don't do it if you have uncommitted work you want to keep.
git reset --hard 0d1d7fc32

# Alternatively, if there's work to keep:
git stash
git reset --hard 0d1d7fc32
git stash pop
# This saves the modifications, then reapplies that patch after resetting.
# You could get merge conflicts if you've modified things which were
# changed since the commit you reset to.

• Note: (Since Git 2.7) you can also use the git rebase --no-autostash as well.

---

git revert <sha-1>

"Undo" the given commit or commit range.
The reset command will "undo" any changes made in the given commit.
A new commit with the undo patch will be committed while the original commit will remain in the history as well.

# Add a new commit with the undo of the original one.
# The <sha-1> can be any commit(s) or commit range
git revert <sha-1>

---

This schema illustrates which command does what.
As you can see there, reset && checkout modify the HEAD.

Another way to get to the deleted commit is with the git fsck command.

git fsck --lost-found

This will output something like at the last line:

dangling commit xyz

We can check that it is the same commit using reflog as suggested in other answers. Now we can do a git merge

git merge xyz

Note:
We cannot get the commit back with fsck if we have already run a git gc command which will remove the reference to the dangling commit.

Try this, This will show all commits recorded in git for a period of time

git reflog

Find the commit you want with

git log HEAD@{3}

or

git log -p HEAD@{3}    

Then check it out if it's the right one:

git checkout HEAD@{3}

This will create a detached head for that commit. Add and commit any changes if needed

git status 
git add
git commit -m "temp_work" 

Now if want to restore commit back to a branch lets say master you will need to name this branch switch to master then merge to master.

git branch temp
git checkout master
git merge temp

Here's also a link specifically for reflog on a Git tutorial site: Atlassian Git Tutorial

This happened to me just today, so I am writing what came out as a lifesaver for me. My answer is very similar to @Amber 's answer.

First, I did a git reflog and searched for that particular commit's hash, then just copied that hash and did a git cherry-pick <hash> from that branch. This brought all the change from that lost commit to my current branch, and restored my faith on GIT.

Have a nice day!

If you cannot find your commit with git reflog and it happen that you were using IntelliJ IDE you can right click on your project root folder -> Local History -> Show History and revert your changes from there.

I messed up doing git rebase with git push -f and this truly saved me since the commit was dropped from the local and remote repositories.

Hope that saves someone's day

Cheers

Sadly git is so unrelable :( I just lost 2 days of work :(

It's best to manual backup anything before doing commit. I just did "git commit" and git just destroy all my changes without saying anything.

I learned my lesson - next time backup first and only then commit. Never trust git for anything.